A very effective way to cheat.
A very good reason to keep poll watchers away from the process.
This might also account for blocks of votes for Biden.
A ballot with only Biden marked on it, scanned hundreds of times, would tend to show such a bump.
In one of the early parts in this long news vid they talk about how it appears there was double scanning caught going on, when exact vote totals were being reported over and over...
Dishonest scales are an abomination to the LORD, But a just weight is His delight.
- Proverbs 11:1
Yet another abomination to the Lord in America...
Computers can be programmed to stop that.