In the example 3p is the LOWEST UNIQUE BID with only one person having placed that bid. 
1p, 2p and 4p are not unique because more than one bid has been placed on them.
5p is unique but it's not the lowest.
What happens if there are no unique bids? If there is no unique bid available the system will then calculate the winner using the lowest bid value with exactly two bids. The first person to have placed the bid will be the winner. If there is no bid value with two bids, then three bids will be used and so on until a winner is established.