What happens when two (or more) scanners count the exact same physical items in the same physical location during a stocktake?

When a scanner counts an item, that count replaces the existing count.  If another scanner counts the same item in the same location, the count from that scanner will also replace the count from the first scanner.

For example, if you have a bin containing 56 of an item, and the first scanner counts 55, that’s what the ABM count will be set to.  If another scanner then counts the exact same item in the exact same bin, but counts 57, the count in ABM will be set to 57, replacing the previous scanner’s count.  What this effectively means is that the last scanner wins – its count replaces any other count.