Note from the data you provided that it even accounted for those who did not vote for President [397] as well as those who over voted [43]:
Times Blank Voted 397
Times Over Voted 43
Suppose that all the computer knows is that there’s a page 1 filled out and a page 2 filled out. How does the computer know whether this is one complete ballot filled out (no undervotes at all), or whether it is one person’s undervote for the Presidential race and another person’s undervote for the amendments (or whatever is on page 2)?