Known problem, scroll back to post
2344 (January 2014) and read forward. Consensus seems to be that you should leave the field blank and deal with it later.
I was hoping I wouldn't have to do that because I just applied for the Business as well(and had no issues with 11 characters), and read they could give you a hard time for having both accounts. I'll give it a shot, thanks.
Also, Lurker said the issue was fixed, so it looks like it has come up again. The old post don't say much on what to do.