Working out average scan time of 100 ballots per minute. Part 2

When Things Go Wrong.
START 11:03:05 END 11:43:00 = 40 min
It took 40 min to scan 13 batches of which 6 were accepted.
600 Ballots ÷ 15 MIN = 40 Ballots per min
25 min lost due to scanner and ballot problems
Actual Ballots counted, 600 Ballots ÷ 40 min = 15 Ballots per min