the sale you are using looks like 38 keys if you sort by time, 2 of them dont match - Seller had a B/O of 39 anyway - http://www.tf2outpost.com/trade/28732882

https://gyazo.com/8185f3bdc230ff5faf1bcfdf730dbb57

Also another sale

Sold for 40 keys - http://backpack.tf/profiles/76561198090956917#!/compare/1485475200/1485561600

So even if the change is small it should include the lower part of the range since it did actually sell for 38 and not 40. I'd re-suggest this at 38-40 and then fix the Cowl that was using this suggestions price.