Nah 3 years he said
He was inside there for more than that I think. The gate was set to break after a certain time period so they had to act quick. But that wasn't about to happen since they were getting picked off quickly and they just didnt have enough power to breeze through it with the time limit they were given. MC's friend had the ability to stop the flow of time inside the gate which is why they were able to last longer and why they were able to keep the gate from breaking. After he died, that ability got passed onto someone else, who continued to stop time from flowing until they were finally able to beat the dungeon. That's why time ran differently while they were inside the gate vs outside. That's also probbly why they didnt age bc their bodies were put into a state of stasis if you will
Why is noone talking about this, did I misunderstand something, or was he inside the gate for 300 years ?!?