Fruit of the LoomFOTL Lady Fit Valueweight T Shirt

Please may i order few shirts, all red but different sizes: s - tom l - sophie m - nico s - lauren m - dominic m- megan s - matt m - amy xs - abi

I am a size 16 and was wondering if anyone could tell me what size I should order, I dont like a tight fit!!

What measurements are XS

Why are sizes in small, medium etc and 10, 12,14 etc , which is for adults ladies??