Repeatable means it can be repeated but I don't know if this applies to events, you'll have to test (usually it just means you can find the same quest more than once).
Higher number = higher chance. See these numbers
<!-- ** Random event frequency (numbers are the base a random number is chosen from, to compare the spawn chance of the random events against) ** -->
if your PostTriggerChance is 5000, you will get the event 100% of the time if you have "More Often" on events and you are past TurnNumber requirement.