When analyzing a fugue, I get confused at times about where to put the redundant entry. Is it the 5th or more entry of the subject and/or answer? I’m not sure.
In a 'textbook fugue' it's an (optional, and not ALL that common - so don't worry if you can't find it!) extra occurrence of the subject in the exposition section of a fugue, after all the voices have stated the subject (or countersubject), So, in a 4-voice fugue it will be the 5th occurrence of the subject.
Not to be confused with anything that happens after the exposition. And not all fugues are 'textbook'.