With the new GEDCOMpare 2.0 system, we process each record in our Gedcoms individually, so when you find that a particular record has bad data (or adds nothing to the existing profile in WikiTree) you should not import the data. The checkbox records your decision to ignore that particular record (i.e., to not import the data).
For background, under the old system, after suggested matches were reviewed, Gedcom records that weren't marked for exclusion were imported in a single batch job. Under that system, you had to mark a record in order to prevent it from being imported. With the new system, it's no longer necessary to tell a computer how records should be processed. Instead, the "completed" checkbox helps us humans keep track of what we've decided and what we've already done. With this new system, however, you cannot avoid making decisions on suggested matches by marking the record as one to be ignored; you have to choose either "match" or "reject" for every suggested match. If you discover later (after processing other records in your Gedcom) that your decision on a particular profile was wrong (maybe you marked a match and you now realize it's a different person), you can go back and change it.
