I found the sizes matched up with clothing she fit.
Size 1 - newborn
Size 2 - 0-3
Size 3 - 3-6
Although she was a teeny tot and those clothes sizes didn't match her age, if that makes sense. So she was in 3-6 clothes til about 7.5 months. Now still in size 4 nappies and 9-12 clothes at 15 months.