I'm guessing he means he had 6 teams and backed 6 fivefolds. If one team drops out then you now have 5 * fourfolds at the slightly increased line per fold. For example, if you had 6 * £1 five folds you would now have 5 * £1.20 four folds.
Hope that makes sense.
Oh but as Adam points out, if the match is rescheduled within 3 or 4 days, the original 5 fold would stand (check with bookie for exact time frame). Although 9 times out of 10 the match is dropped from the bet.