I'm a new GM and after running a session where two named NPCs were defeated before even having a turn I started to question if I was doing something wrong. One of my players (who GMs as well) asked if I was adding the dice HP to the monster's HP total. He said for his games he takes the HP and then rolls all the dice in the HP part of the stat block and adds that in. I did that for the last boss of that dungeon and it seemed like the fight lasted about as long as it should. Her stat block shows
hp 59 (6 HD; 4d8+2d10+26)
I ended up with 104 after rolling and adding to the 59.
Now in prepping for the next session the way the stat blocks are worded makes that not seem correct. I have been left to question myself and my understanding of the rules. After running a quick sim of the dice from that block I do get 59 on average. Is 59 just the average that would happen that I can use instead of rolling or am I supposed to be doing something more to get a higher number? My bosses seem to be going down to easily but adding the rolls to the HP just doesn't seem right.