It appears that your polygrapher used the relevant/irrelevant technique with a math question tacked onto the first series as a sort of "control" question. This is sometimes done during an R/I "test" when the subject shows little reaction to any of the relevant questions, in order to see if such a question will produce a reaction. Another technique that may be used for this purpose is for the polygrapher to deliberately mis-state one of the irrelevant questions. Suppose your date of birth is 30 August 1980, and this has been reviewed with you as one of the questions to be asked. The polygrapher might deliberately mis-state your date of birth, asking, "Were you born on 30 August 1981?" Again, the purpose is to see if you will produce a reaction to the question.