Ch 54: A Little Break
But before going to the fifteenth floor, the conqueror decided to take a little break. Even though not much time had passed in the outside world, they had stayed inside this dungeon for quite a long time with the time dilation.
If this was a dungeon where they had to start from the beginning after going out, then they obviously would not leave it halfway before completely clearing. But as that was not the case and it was possible for them to just go out for some time and then come right back to where they left, it made sense for them to take a little breather here and there.
Actually Rein was planning to take a break after clearing the thirteenth floor, but as the dungeon master was made to lower the difficulty of the dungeon for some time after that floor, he was kinda forced to continue in order to take advantage of that, as not doing so was foolish.