If I recall correctly:

- JN/ZN/YN/HN track J/Z/Y/H exactly

- IN has been observed to sometimes be greater than I (otherwise equal)

- XN is frequently observed to be greater than X (otherwise equal)

- PN used to track P exactly (until a couple months ago) but no longer does (is equal or less than P)

- RN used to sometimes be greater than R, but hasn't been seen in a while, and is rarely booked into (a few reports with non-standard upgrade clearing booking into RN)

- ON is not always equal to O, but I forget which way the difference goes