Do this little experiment:
put it in the center of the room. level it as good as you can by the bubble. go to the wall and put a pencil dot there.
go back and make it unlevel again. now, relevel it. do not look at the dot on the wall. go see how close it is to the dot.
a bubble is hard thing to get just right. it can look right, and be off, and if you multiply that out 20 or 50 feet, it grows.
you can swing it around on the tripod, but the chances of getting it level in every direction are small.
in a room, the best level is one that has a diffuser. a laser beam is projected. mirrors scatter it around the room to make a line, either horizontal or perpendicular. a weight makes it true plumb. if you smoke, blow smoke into the laser light to help understand what the laser is doing. if you need a line high or low on the wall, shoot anywhere on the wall, put a pencil mark at each corner, then measure up the same distance from the mark to where you want to be and pop lines.
diffusers are better to use when you need a line around a room. the torpedo type you have is better when you need a straight line. I have found that they work great on some things, but not all things, because they go off on a timer, and you have to keep turning them on, and the slightest bump, and they are out of whack from where you want to be.
they do have their uses and areas where they shine, but it takes a while to get the hang of them and how they work. sometimes by the time you get through fooling with them, you could have done it the old way.
Steve