If there are two identical bids, it may be due to an automatic bid made by a previous bidder. The automatic bids can be the same amount as a manual bid from another bidder.
On the other hand, it may be because two automatic bids at the same amount have been placed. In both these cases, the (automatic) bid that was first placed will be considered as the highest bid.
The picture shows two similar bids. The top bid is the highest as it is placed first (as a max bid).