Since no complete audit of ballots are done, the hand count would match the machine count.
Originally the tabulator was suspected of keeping vote count of a favored candidate ahead by a few percent. This was supposed to an incremental process. The vote stuffing and dumping could have proceeded without raising any suspicion.
However, if the opponent is leading by a higher margin than expected, more stuffed forged votes are needed to be injected. That is why you can see sudden spikes of Biden votes.