The jumper tables have nothing to do with height, it's the classification of rules on how you will jump your course, particularly when you do the jump off.
Looks like all of your classes will be Table II, Section 2(b), which is also known as "timed first jump off". I think most non Grand Prix jumper courses use this table. If you're clear of any faults (including time faults) you stay in the ring -you are allowed to stop but can't leave the ring- and when you hear the buzzer, you continue to your jump off. You have 45 seconds from when the buzzer goes off to get to the first jump off fence. If you weren't clear in your first round you leave the ring and skip the jump off. Ribbons are ranked by the least amount of faults, starting with those in the jump off. if there is a tie for number of faults it is ranked by speed (faster is higher) So if you knock a rail down you get 4 faults, but you want to be the fastest 4 faulter out there! If they have more ribbons then people who got to the jump off it is based on time for the next group from the first round with the least amount of faults. Always look at time if there is a tie for faults.
I don't remember all of the tables but other ones you might see:
Table II, Section 2(a) -aka 'timed first round'. All you do is your first round, and there is no jump off unless there is a tie for first.
Table II, Section 2(c) -is probably the next most common. it's also known as "power and speed". Somewhere in your course is a designated finish line. You begin your course (power phase) and if you are clear you -without stopping- begin the speed phase. So it's like one giant course but you start off more carefully and somewhere in the middle you should pick up the pace a bit. If you are not clear in your power phase they buzz you out and you leave the ring without doing the speed phase.
Sorry if that's kind of confusing!! There are a lot of rules! Once you do a couple of jumper shows you'll get the hang of how the tables work and the best strategy for each. I've only been to a few shows that had something more then 'time first jump off' and/or 'power and speed' so you don't need to memorize all the tables. Often at multi-day shows (like rated shows) they'll do one table one day and another table the next.
Let me know if you'd like me to clarify anything more! I'm not sure my desription made a lot of sense....