This is a baby/toddler cardigan pattern that is knit flat from the top down. The sizes are determined by the needle size you choose (US 1 & 3 for 6 month size, US 2 & 4 for 1 year size and US 3 & 5 for 2 year size).

For stitch gauge,

7 st/inch on US 3
6.5 sts/inch on US 4
6 sts/inch on US 5

There is no additional information on row gauge.

The pattern also suggests these yarns as possibilities:

Tess’ Designer Yarns in Peruvian Sock, Twinkle Toes, Whiskers, Superwash Merino Petite, as well as the Baby Bunny or the Superwash Merino & Superwash Merino Lace held together.