Is a 7.7 mpv low and if so what does it indicate?

Probably normal: Depends on the lab. Even if it's a bit out of the reference range, remember that this is simply the range where most-but-not-all asymptomatic couch potatoes fall. If your physician isn't concerned, you certainly should not be. We pathologists in the lab say, "treat the person, not the numbers." glad you're proactive.

Slightly low: Mpv is mean platelet volume. Is reflects the size of the platelets. Young platelets are bigger and tend to shrink as they age. They live an average of 7 days. Lower mpv may mean that your platelets live a little longer or produced little smaller.