As others have pointed out, since you have only provided evidence of a 16 key sale, you should have suggested this at 16. You cannot have 15 as you have provided no proof or reason to include it.

However, there are many more sales to look into:

https://backpack.tf/profiles/76561198095407289#!/compare/1597017600/1597104000

https://backpack.tf/profiles/76561198172191039#!/compare/1597104000/1597190400

Sold for 6 keys

https://backpack.tf/profiles/76561198172191039#!/compare/1599004800/1599091200

https://backpack.tf/profiles/76561198129143307#!/compare/1599004800/1599091200

Sold for ~6 keys

https://backpack.tf/profiles/76561198129143307#!/compare/1600214400/1600992000

https://backpack.tf/profiles/76561199039289574#!/compare/1600300800/1600387200

Bulk

https://backpack.tf/profiles/76561198129745094#!/compare/1596240000/1596326400

https://backpack.tf/profiles/76561198012537041#!/compare/1596153600/1596240000

https://backpack.tf/profiles/76561198060742533#!/compare/1596153600/1596240000

https://backpack.tf/profiles/76561198126695508#!/compare/1596240000/1596326400

Bulk / untrace

https://backpack.tf/profiles/76561198126695508#!/compare/1596326400/1596412800

https://backpack.tf/profiles/76561199011488010#!/compare/1596153600/1596326400

https://backpack.tf/profiles/76561198011707565#!/compare/1596240000/1596412800

https://backpack.tf/profiles/76561199011488010#!/compare/1596326400/1596412800

https://backpack.tf/profiles/76561198850121720#!/compare/1596326400/1596412800

Untrace

https://backpack.tf/profiles/76561198850121720#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198966838493#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561199011488010#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198966838493#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561199011488010#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198966838493#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198279706201#!/compare/1596499200/1596672000

https://backpack.tf/profiles/76561198011707565#!/compare/1596585600/1596672000

https://backpack.tf/profiles/76561199027438666#!/compare/1596585600/1596672000

https://backpack.tf/profiles/76561198850121720#!/compare/1596585600/1596672000

Tradeback / bulk / QS

https://backpack.tf/profiles/76561198386716854#!/compare/1597536000/1597622400

https://backpack.tf/profiles/76561197970869719#!/compare/1597536000/1597622400

https://backpack.tf/profiles/76561197970869719#!/compare/1597708800/1597795200

https://backpack.tf/profiles/76561198094190043#!/compare/1598400000/1598572800

Bulk

https://backpack.tf/profiles/76561198094190043#!/compare/1598745600/1598832000

https://backpack.tf/profiles/76561198084813853#!/compare/1598572800/1598745600

https://backpack.tf/profiles/76561198106372188#!/compare/1597881600/1598745600

https://backpack.tf/profiles/76561198089830691#!/compare/1598572800/1598745600

https://backpack.tf/profiles/76561199081277857#!/compare/1598745600/1599264000

https://backpack.tf/profiles/76561198063536945#!/compare/1598659200/1598745600

https://backpack.tf/profiles/76561198864760524#!/compare/1598918400/1599004800

https://backpack.tf/profiles/76561198129342342#!/compare/1515542400/1599004800

https://backpack.tf/profiles/76561198268703524#!/compare/1598918400/1599004800

https://backpack.tf/profiles/76561198210372209#!/compare/1598918400/1599004800

https://backpack.tf/profiles/76561198832761255#!/compare/1599004800/1599091200

Untrace / Bulk / QS

https://backpack.tf/profiles/76561198832761255#!/compare/1599091200/1599177600

https://backpack.tf/profiles/76561198453331821#!/compare/1599091200/1599177600

can trace 4 keys

https://backpack.tf/profiles/76561198453331821#!/compare/1599609600/1600214400

https://backpack.tf/profiles/76561198832761255#!/compare/1600128000/1600214400

Untrace

https://backpack.tf/profiles/76561198832761255#!/compare/1600387200/1600473600

https://backpack.tf/profiles/76561198830746068#!/compare/1600387200/1600473600

Untrace

https://backpack.tf/profiles/76561198830746068#!/compare/1600819200/1600905600

https://backpack.tf/profiles/76561198127742823#!/compare/1600905600/1600992000

Sold for 16 keys (your sale)

https://backpack.tf/profiles/76561198850121720#!/compare/1600214400/1600300800

https://backpack.tf/profiles/76561198864760524#!/compare/1600214400/1600300800

https://backpack.tf/profiles/76561198037674114#!/compare/1600300800/1600646400

Bulk / untrace

https://backpack.tf/profiles/76561198037674114#!/compare/1600300800/1600646400

https://backpack.tf/profiles/76561198830746068#!/compare/1600819200/1600905600

Untrace / QS

https://backpack.tf/profiles/76561198830746068#!/compare/1600905600/1600819200

https://backpack.tf/profiles/76561198188229086#!/compare/1600905600/1600992000

Sold for 16 keys

https://i.imgur.com/hxNfJrN.png

Bot.tf shows 2 sales for ~16 keys, one for ~6, one for ~7 keys.

so in total, sales are @:

6, 6, 6?, 7?, 16, 16 keys

the huge disparity in sales with nothing to point to which ones are the outliers tells me this should stay outdated.