Inside the virtual reality,
After getting the health recovery Allen decided to fight some monsters. So after searching for some time, he found some snakes. All those monsters are the same as the monsters that Lisa was previously fighting.
After finding those monsters Allen decided to fight them because he already knew the weak point of those Monsters.
After finding those monsters Allen did not attack them instantly, he waited for the right time to attack those 3 snake monsters. Also mostly those Monsters were above level 25. This is also one of the reasons he decided to attack them. He did not want to fight any powerful Monster that was above level 30.
Even though he wasn't able to check the level of those monsters using his system, he could feel the spiritual energy that those monsters were releasing and because of this, he came to the conclusion. He could be wrong but he was sure that he could win against them.