The events are “AP_ALT_VAR_INC” and “AP_ALT_VAR_DEC”, and they correspond to a single “tick” of the (default) rotary switches. The event list is called “Legacy Events”, Perhaps because they did not add new ones beyond the old FSX ones. In those days the amount that stands for a “tick” was dependent on how fast you were turning, increasing step size if you appeared to be trying to cover a large “distance.”
Cheers,
Bert