It depends. Once the results come out, we figure out how many offer-holders have achieved their grades. If there are still places remaining, then we start to look at "near miss" candidates. We'll take the top near-miss candidates until we either run out of places or of suitable people. Ranking is done based on point scores or sometimes individual subjects - it's hard to say exactly without knowing the people and places available. Historically, we usually take a single digit number of "near miss" candidates, but of course that's not a guarantee that there'll be any room left in the coming year.
In recent years (1617, 1718) competition for places has meant we have not generally been able to accept near-misses.