Strange question totals in interview editor

In the interview editor (and in the API interview stats call) I get the following numbers:
Filter Questions

The groups seem to consist of complementary categories, so they all should amount to the same total question count. They don’t:

Group . . . . . . . . . Total
Valid/Invalid . . . . . . 109
Not/Answered . . . . 101
Super/Interviewer . . 99

How do these differences come about? What is the actual total question count in this interview?
I need to use these figures in a program which verifies the interviews and then either rejects or approves them.



Not precisely, a question can be hidden, for example, and this ruins this beautiful picture as it will not belong to either interviewer or supervisor groups. Similarly, whether it was or was not preloaded is not of a concern of the interviewer, nor even the supervisor.

The total number of questions in a questionnaire is shown in the questionnaire settings:

In any particular interview it may differ (can be larger due to repetitions in the rosters or lower due to enabling conditions).

Thank you, Sergiy. I had thought of the identifying questions. But they are counted in both the 109 Valid/Invalid group and the 101 Not/Answered group. I hadn’t thought of hidden questions, they could explain the difference between the Not/Answered group and the Super/Interviewer group…
But I conclude from your reply that these categories are not complementary then.