Use your race install like a slide hammer.....when the race is properly installed you'll know it.

Ting, ting, ting, thud.

If there's a gap there's a gap. The question is why is is there a gap and is it going to bother you?

If your fork spins freely the race is probably squared properly and its just the seat that's not machined 100%. No big deal as I've plenty like this and it poses no problem.