If you have spilled grease or oil or cheese reside on the bottom of your oven - wipe most of that off/up before starting the cleaning cycle. (Ever bake a home-made pizza with lots of cheese and it drips? or scalloped potatoes that bubble over?)
The spills could catch on fire.
When I use the cleaning cycle - not very often - I do like to stay "nearby" - but not in the kitchen with it - it stinks when it is doing its thing.
Either open windows or keep the vent fan going.