MDB08M is the latest build available as a full re-flash (loosing your data) from the factory images page (Here:
https://developers.google.com/android/nexus/images?hl=en)
I don't think anyone has recieved an OTA (over the air - as in a smaller update delivered by wifi or 3g to your device, and can be upgraded too without a full reinstall) update for it yet, most people have MDB08L (Nov) so far, but some still have the October MDA89E build.
Its not worth worrying about.. itll keep itself up to date as designed as long as you are running a google blessed build.
When updates get pushed out they are released in stages (based on some internal id like serial or IMEI), so yuo wont necessarily get it the same time as others.