Concord/WordList mismatch
If WordList finds a certain number of occurrences of a (word list) cluster but Concord finds a different number, this is because the procedures are different. WordList proceeds word by word, ignoring punctuation (except for hyphens and apostrophes). When Concord searches for a (concordance) cluster it will (by default) take punctuation into account: you can change that in the settings if you wish.
