WRUU925

I'm trying to create an account on repeaterbook.com and having problems with creating a username for some reason everything I put is wrong I asked the question to repeater book admin and he sent back his username so I made one similar and then I got the message saying this username cannot be found now that just blows my mind because I'm creating it now, so I know it's something simple but I just don't get it can someone give me an example this is the one I was trying to create SE7EKI/GWULF77 the admins username was similar to this one same amount of characters.

Got it all figured out now