If there's only one sale, there shouldn't be a range. For items with a range, take the midpoint of that range for valuing that item (e.g. an item at 50-60 would be taken at 55).

The seller who sold it to you had a buyout of 120 keys https://gladiator.tf/time-machine?item=Starstorm+Slumber+Slo-Poke&at=2022-09-20T20%3A36%3A00.000Z, so the sale can't be valued at more than that.

As for mini-ing the MF Nunhood, there looks to be an older sale

https://backpack.tf/profiles/76561198088878793#!/compare/1660694400/1660953600

https://backpack.tf/profiles/76561198034850359#!/compare/1660867200/1660953600

https://gladiator.tf/time-machine?item=Massed%20Flies%20Nunhood&at=2022-08-17T10:20:01.000Z

This looks like 38 keys but the buyout was 40, so may be worth asking the buyer/seller for confirmation

(since this sale is more than 3 months old, you can't use it to make a suggestion for the Nunhood by itself, but you can use it here to estimate its value for this suggestion)

If you took 40 for the Nunhood, you could value this sale at 60 + 40 = 100 keys