YOW P1 Parking with Visa Infinite Privilege Card

I'm looking to clarify the process since it appears I'm not supposed to book online if using the Visa card. Instructions say to drive in, get a ticket and park on level 3. If there's a Visa spot I can park. If not, I assume I should park where I get a spot. That part isn't noted but seems obvious.

Later it says to bring ticket to parking office where I pay on the spot and get a 20% discount at that time. It doesn't say whether to do this when I arrive or leave. Again, I assume when leaving but it's not noted and opposite to what you do if you reserve ahead.

Anyone recently done this?