In answer to your question
If you have more than one precinct voting at a location the scanner must be programmed to read ballot for each district. Down ballots are often different. Their ore the location of vote varies. Local races (school board- county offices etc vary radically within a county. . All races must appear on one page so font size and spacing often vary Thus two different machines may be needed to read different precincts voting at one location.
IMO this is why so many ballots only voted for Biden. They couldn’t line up the remaining contests to the various voting machines on the fake ballots So it was designed to read only one. The first one.
Thank you.