After killing those 5 grasshoppers Allen begins to advance once again. As you can tell he really wanted to know how to spawn the Boss more quickly. Without killing the boss he won't create a new dungeon. So because of this he already decided to kill all the monsters in the floor once again.
Even though those Monsters were level 25, none of them has bloodline greater than bronze grade. So, killing them became easy for him. He will need it just one day to kill all the monsters inside that floor. Actually you will not kill all the monsters because 20 minutes later those Monsters who previously got killed will respawn. But for him he will kill all the monsters.
After one day later,