Why is sub-infotype of IT2002(Attendance) not in T591A??

I once thought every IT-SubIT mapping is stored in T591A. But I find that some IT like IT2002 have no sub infotype records in T591A, but still, we can find their sub-infotype in pa20/pa30 T-code.

So my question is: How to modify sub-infotype for those ITs which is not in table T591A?

Thanks in adv.