PAS 0 provides no pedal assistance but 100% of the throttle is available.
PAS 1-3 have lower levels of assistance. 1 and 2 offer a "choose how hard you want your work out to be" situation. 3 is a moderate boost, and 4 and 5 really step it up. The jump from 3 to 4 and 4 to 5 really provides some oomph in the higher PAS settings. To generalize, PAS 1 starts at around 40% and the intervals go up on average 15% from there, with the nuances mentioned above. For each PAS, throttle DOES NOT supersede the max output for that PAS level. For example, if PAS 2 has an output of 55%, you will have 55% usage of the throttle when pedaling. When not pedaling but still in the same PAS, you will have 100% access to the throttle. Of course in PAS 5, this won't matter because it is set to 100%.