Pattern is written in US crochet terms.

This tank is worked from the bottom up in 2 pieces (front and back) and then seamed together.

Sizes are referred to in order when given instructions in parentheses throughout the pattern.
30(34, 38, 42, 46, 50, 54, 58, 62)

I highly recommend a yarn that has some some drape and stretch (including fibers like bamboo) for fit as shown.