In Barn Hunt, which of the A/B classes can I enter?

Here's Barn Hunt's official guide to A and B classes (opens in a new tab)

IMPORTANT NOTE: The table below shows the classes you can enter. HOWEVER, you may only enter one class level for an event (weekend). So, for example, if you enter Open-B on Saturday, you can only enter Open-B on Sunday. You may not enter Senior-A on Sunday (Rules Part 12, Section 1(b)). This all changes if you get a title during an event!
My dog's highest BH title is:
I can enter:
Any title, including no title
Crazy-Eights
Crazy-8s is a non-regular class open to all dogs with a BH number. You can enter Crazy-8s in addition to your regular class(es) at the same trial.
no title
Instinct and/or Novice-A
You CAN enter BOTH Instinct and Novice-A at the same trial.
You CAN enter JUST Instinct.
You CAN enter JUST Novice-A. You do not need a RATI title to enter Novice-A.
Remember that your dog has to be registered with Barn Hunt Association, and you must have its BH number.
RATI
Instinct and/or Novice-A
You CAN enter BOTH classes at the same trial.
You can keep re-entering the Instinct class (even if you already have a RATI title) until your dog achieves RATN.
RATN or RATNX
Novice-B or Open-A
You can only enter ONE of these classes per trial/event (weekend), NOT both.
RATO or RATOX
Novice-B or Open-B or Senior-A
You can only enter ONE of these classes per trial/event (weekend).
RATS or RATSX
Novice-B or Open-B or Senior-B or Master-A
You can only enter ONE of these classes per trial/event (weekend).
RATM, RATCH, RATCHX
Novice-B or Open-B or Senior-B or Championship
You can only enter ONE of these classes per trial/event (weekend).