Hello,
Because in a real oven that goes up to 420°c- 500°c, the pizza is ready in 60-90 seconds.
Unfortunately, this one is electric and hardly reaches 400°c.

So basically they've calculated that a pizza cooks in 5 minutes.
For a better result, go to "ooni".

5 min because it generally takes less than 5 min until the pizza is done. The levels correspond to a specific number of degrees and for specific purposes as described in the operating instructions. Pizza needs the highest level.