Typically your bib # corresponds to projected finish time...so if you provided a time with proof (Name of Race on registration I am guessing) then theoretically the lower your bib # the faster you are are projected to finish. If your 10k time is slower than mine, then seems like your number would be higher, not lower - because theoretically my pace is a little faster or was on the race I submitted

. BUT honestly who knows if they truly mean anything. May not be the case this year as there do seem to be some people with numbers NOT matching this. This has been the case in the past....lower numbers equated to faster submitted 10k or 1/2 times.
That being said, if you want to be sure you are in a "faster" corral in line with your pace, take a copy of race results with you to the expo.
Oh and I am NO expert.....still not sure how I was in Corral B last year, but apparently my time submitted was fast enough.