Our top bunk is rated for 250 lbs. It is above a similar size bunk and is partially enclosed by the bathroom wall. It reminds me of the railroad car sleeper bunks depicted in old black and white movies
Visually, it looks sturdy since it is connected to a wall, and I think the fact that the bottom bunk is the same size helps as well. If your bunk open and is over a similarly open sofa, it may be an optical illusion that it is unsafe.