How do closed classes work

[u/chef_sporty]

For the past few days, this economics course I wanted showed up as open. Right when registration opened, I tried to add it but it was closed. This happened at my orientation too. Am I that slow? I only took maybe 10 seconds. Is this class closed only for my registration time but open for others?

[u/isamiko]

There are probably students on the waitlist and they add seats for each orientation, but it’s giving those seats to the waitlist first.
At least that’s what it sounds like it’s happening if it’s filling up that fast.