How to kasher an oven that absorbed the taste of challah

I accidentally burned the challah in the oven I was baking it in, so I asked my rabbi and he told me to turn the oven to the highest heat for 20 minutes. The thing is, I have a convection oven that can reach up to 500 degrees, do I have to turn it on all the way to that heat?

Dear ...!

There is no need to run the oven on a self-cleaning cycle, since you did not use the highest heat when you baked the challah. Therefore, you should set it to the highest heat setting used for baking (usually 250 degrees).