ok. i can't stand to count stitches or whatever when i'm crocheting. i lose track too easily.
so. how does the hat look like it will fit on your head. put it on and see what it's like. if it isn't small start doing all singles now. it might take a row or two before you start to notice it really come in so keep that in mind.
iif after a few rows it's for sure not going to fit your head, you're going to have to take the rows out and make it bigger. it will hurt to destroy your hard work but it'll go away as soon as you start going again.
if it's too big you can either take it out a bit and start singles sooner or just skip some stitches as you go and hope it turns out ok. really, a hat isn't super complex and it stretches and stuff so your mistakes won't show much. just go for it.
remember: singles make it curve in
doubles make it flat
skipping makes it curve faster
that's all you need to know.