The numbers inside [ ] are for different sizes. For the smallest size you knit 1, for the next size, knit 2, etc. It's helpful to circle the numbers for the size you're making to recognize them quickly and easily and reduce confusion and errors.
Cheating is an option. . . . Cheaters never win and winners never cheat, but smart knitters who want to retain an iota of sanity do, cheerfully. ~~Kory Stamper