Ok...I’m really not trying to be dense...you’re saying if there are 100 precincts, the bar under “1” represents the vote tally from all precincts where the first digit in that precinct number is “1”, e.g. 1, 10-19, 100?
If there are 100 precincts, there would be 100 total Biden vote tallies, if you take those 100 numbers and look at each numbers’ leading digit, you would expect 30 of them to begin with the number 1, and about 18 to start with the number 2, and so on and so forth.
When people are making up numbers though, they rarely follow this pattern. That’s often how fraud detectors can quickly look at a set of records and immediately suspect fake made up numbers instead of real life data.