I don't include brainstorming in the 3 hours. That means creating the concept and features that don't necessarily change the game itself. For example, I added three more languages that weren't strictly necessary and didn't change the game, but they help the testers understand what it's about. I also wouldn't include a tutorial.
If you're just thinking about whether something looks better here or there and doing several in-game tests, I wouldn't include that time in the time limit either, because that's more in line with concept development.
Creating and positioning graphics, creating 3D models, writing scripts, and creating and implementing sounds are tasks that change and expand the game. For me, that falls under the time limit.
But that's just my opinion. Don't let the 3 hours stress you out. If you can honestly say to yourself that you only felt it took 3 hours, even if it was actually 30-40 minutes more, I think that's perfectly fine for everyone.