You don't say what control you are using, but the explanation from the 18iT-B manual seems to agree with what you say.
The R value is the distance from the current Z position to the start of the tapping feed.
The P value is the dwell time, although I've never programmed a tap cycle with a dwell. It has 4 digits because P can't have a decimal point. P1000 would be a 1 second dwell (.001*1000)
R can have a decimal point.
I believe if you're going to use rigid tapping, you'll need an M29 S#### in the block immediately preceding the G84.
G84 Z-1.25 R.2 P1000 F0.0909