What does the size indicate? Bust? Waist? Hips? and for what age?
Why is the size left to guesswork?
The material is elastic enough to accommodate some plus/minus, so wouldn't it be sensible to just indicate the [average] age?
Bought size 30" for 10-year old, turned out to be tight but keeping it for a 7-year old (slightly loose but will be a perfect fit in a few months' time).
Now to the next guesswork: getting size 32" in the hope it would fit a 10-year old.
Please note that the kids in question here are a size or two ahead in their school uniform size (i.e., a bit taller for their age) just in case you take note of the info above.
This swimsuit is of good material and reasonable price, unfortunately, the annoyance with the confusing size just clouds over the good aspects of this quality swimsuit.
Having received and tried it on, size 32 is a good fit for a 10-year old. From experience so far, the following may be a better guide than what you'd find with the most confusing chart.
Size 28: Perhaps 6/7 year old.
Size 30: 8/9 year old (label says 10-year old but we now know it's very tight!)
Size 32: 10/11 year old (label says 12-year old which seems inaccurate!)
Size 34: Perhaps 12/13 year old.
Once again, please note that the children who tried on the swimsuits are a bit taller for their age, so factor this in if you make use of this info.