Order numbers sequel sometimes jumping

[Burgess]

I also see an unconsistancy in the virtuemart_invoice_id table, a jump from 681,682,693,694 etc.
The orders after the jump is new test orders only. Tried the "repair table" i phpmyadmin - but it still jumps in the sequence
  - I actually solved this using - Repair table in phpmyadmin and then changed the AUTO_INCREMENT to correct value - but still the same error.