You're not alone. I've been around a long time and I don't understand it.
Very few people have more than a rough idea about how that all works.

Our trip rigs, duty rigs and rotation guarantees are VERY important however.
That's what prevents the company from abusing us worse than they already do with horrible unproductive low paying trips, excessive sit arounds, multi-day layovers for no pay, etc. etc.

The rigs haven't got much attention over the last couple contract cycles because we've had other priorities but they are the bedrock of our quality of life.

I understand in this cycle the negotiators explored trying to get a flat daily guarantee instead of an average daily guarantee.
They couldn't get it. The price management wanted would have been too high.