My Crocs are a size 4/5 (the smallest ladies size) and they fit wonderfully. I have yet to see real Crocs that are sized S,M,L,XL. I have noticed that they do have a variety of sizing formats. My Croc sandals are a ladies 6 (no mix sizes) and my son has a pair of "just 6" ladies size, not the 6/7 that his sister has. And my lace up Crocs are a size 6, too but dh's Professionals are a 10/11. I'm not sure why they are all different. Some we bought online and some we bought at a local shoe store. Try a pair in your "real" size and see if that doesn't help.
Are the Converse's realy clear? It's hard to tell in the add. I'm presuming I'm seeing the inside footbed? I'd like to see these in person. My dd would really get a kick out of clear converses! But $50! Ouch!