This looks like it could need an update

Sale #1 - 11 keys

https://backpack.tf/profiles/76561198069969998#!/compare/1545955200/1546300800

https://backpack.tf/profiles/76561198164318881#!/compare/1546214400/1546300800

Sale #2 - gonna guess 13 keys -

https://backpack.tf/profiles/76561198164318881#!/compare/1546473600/1546560000

https://backpack.tf/profiles/76561197975749074#!/compare/1546473600/1546560000

Sale #3 - 15 keys

https://backpack.tf/profiles/76561198442764620#!/compare/1546473600/1546560000

https://backpack.tf/profiles/76561197975749074#!/compare/1546473600/1546560000

Sale #4 - Sold with a key for a Stormy Sky High?

https://backpack.tf/profiles/76561198442764620#!/compare/1546560000/1546732800

https://backpack.tf/profiles/76561198246285078#!/compare/1546646400/1546732800

Sale #5 - Less Then Buyers ( 6 keys + Victory lap )

https://backpack.tf/profiles/76561198246285078#!/compare/1549238400/1549670400

https://backpack.tf/profiles/76561198034732229#!/compare/1549584000/1549670400

Sale #6 - Ausi Frontier + 3 keys in sweets

https://backpack.tf/profiles/76561198034732229#!/compare/1549843200/1549929600

https://backpack.tf/profiles/76561198134319050#!/compare/1549843200/1549929600

Taking 9.5 + 3 = 12.5, rounded to 13

Sale #7 - https://marketplace.tf/items/319;5;u7 - https://backpack.tf/item/320216935

20 / 1.75 = 11.4 keys

Sale #8 - Untrace

https://backpack.tf/profiles/76561198240537922#!/compare/1548028800/1548115200

https://backpack.tf/profiles/76561198302161698#!/compare/1548028800/1548115200

Sale #9 - 9 keys (Histories Counted)

https://backpack.tf/profiles/76561198302161698#!/compare/1548115200/1548547200

https://backpack.tf/profiles/76561198858353310#!/compare/1548201600/1548288000

Taking 11 - 15 keys