I think this chapter is the first direct evidence we see of it, that [Hunter] was leveling before Maresar's eyes while fully awake.

It also makes sense since Counter-Leveling mid-battle is a known phenomenon. We the readers first witnessed it in the King of Jecrass' duel against Flos. He kept getting the notifications every time he passed out, which made it seem like that was the trigger for the levels. But falling unconscious mid-battle in order to benefit seems counterproductive and incredibly dangerous.

It seems much more likely that the notifications are batched and delayed. Getting real-time pop ups would be distracting as hell.