I'm trying to figure out the whole heal Point system. Reading the MPA site is confusing.

Can anyone put it in simple terms. Premlinary index is how many tourney points you are worth to oposing teams correct?

So let's look at John bapst they have a pi of 8.4444 so let's say today Belfast who has a pi of 1 played them and beat them. Belfasts PI would now be 3.1? Going up 2.1 with the win? That would put Belfasts TI at 4.6913? Am I right or wrong? Would this loss do anything to John Bapsts pi or ti?