With a very large word-list, concordance etc., you may wish to reduce it randomly (eg. for sampling). This menu option (Edit | Deleting | Reduce to N) allows you to specify how many entries you want to have in the list. If you reduce the data, entries will be randomly zapped until there are only the number you want. The procedure is irreversible. That is, nothing gets altered on disk, but if you change your mind you will have to re-compute or else go back to an earlier saved version.