I've attached an image containing 3 screenshots:
1. Database & design settings
2. Field & validation settings with UserEmail selected
3. Field & validation settings with UserFirstName selected
If I choose the correct settings for UserFirstName, move onto another field, then back again to select the UserFirstName field, it reverts back to the incorrect 'email address' validation settings.
I've tried on 2 different computers with different site definitions, same problem.