Bootees are not one of the first twelve in the book and are not considered the Nursery rhyme bootees i.e. you will not need the 1st ten rows of the Baby Bunting pattern to make this pair - the website gives the first ten rows, ignore it.

Sizes are not specified in the pattern, but the following is suggested:

Birth to 2 months: size 2.75 mm/US 2/UK(Imperial) 12 needles, to make a 10.2 cm/ 4” bootee.
3 to 6 months: size 3.25 mm/US 3/UK(Imperial) 10 needles, to make a 11.4 cm/ 4.5” bootee.
6 to 9 months: size 3.75 mm/US 5/UK(Imperial) 9 needles, to make a 12.7 cm/ 5” bootee.

Any 3-ply or baby wool is suggested in the pattern.

For more information, see:
https://vintageknits.wordpress.com/category/bootees/page/2/