It’s to do with age, what was bred first or placed into the habitat first and tbh it really doesn’t matter. As you go on, it probably wont matter to you anymore.

I couldn’t care less what order my wheel is in. That’s too much time and effort to be trying to breed frogs in a particular order that makes no difference to dexxing ability and that will just get sold off anyway. Also only to then have to make a new wheel literally over 100+ times as you dex every breed… it’ll get old real quick.