I've posted the same, but with their respective "summaries" of size in basic wording, in case you wanted to know...
32x32 - Tiny
64x64 - Tiny
128x128 - Medium
192x192 - Extra Large
256x256 - Huge
384x384 - Gigantic
512x512 - Gigantic
Custom - Varies, based on 2nd number it seems...for example: 512x32 was Custom, but appeared as "Tiny" in the list.
No idea why they used duplicates...they could've made 64x64 "Small", 192x192 "Large", 256x256 "Extra Large" and 384x384 "Huge" while leaving 32x32 as "Tiny", 128x128 as "Medium" and 512x512 as "Gigantic".
But...that's the way it is at the moment if you wanted to know.