You do know there are multiple ballots during elections, right? Like, my region had 4 that I could cast.
The key phrase in your document there is "All Contests" and perhaps even "Unofficial and Incomplete"
And even then your document makes no sense since it appears to claim there are less than 600,000 registered voters in America across the 328.2 million people we have living here? So that document is either whack or looking at a single state.
It's just a specific region. But fine fair enough. Multiple ballots per election.
However there are anomalous factors here.
The total sent are 811,836 and theres 2 ballots per voter.
The registered voter count is 408,268. And if you double it you get 816,536.
816,536 - 811,836 = 4700.
4700 Ballots missing, right on the dot.
2350 people's votes missing, at least. If there are not false votes that have taken their place.