Floor of tests

How exactly do the Regular “waves” work in Tower of God?

Once a group of Regulars clears the 1st Floor, does that automatically open the way for a new wave to begin? Or do new Regulars only start being selected after the previous wave finishes all the floor tests?

I tend to think the first option doesn’t make much sense, since that would imply that Headon is dealing with dozens of Regulars simultaneously.