Trish, how much overlap do you have; have you measured it? 12.5mm is 1/2 inch; will that even help?

The posters who have said that overlap is not unheard-of are correct, but that doesn't make it any easier for you to ride, especially if it makes you uncomfortable. I suggest you talk further with the folks who fitted you and see if they can come up with a more acceptable (to you) answer.