Vin# versus Build#

[1987 GN]

I noticed that the build # of my car is higher than some of the other TTAs on sites like ebay yet the last 6 digits of the vin# of the other TTAs is higher than mine. So what I am asking is "Is it possible for the build # sequence of the car to not be in sequential order according to the vin#?" I posted this on turbobuick.com but I have not gotten any responses. Any ideas? I have a letter the original owner got from PAS that says my build # so I did not think it was wrong.