Or they just wiped 20k trained men off the board which was enough to weaken an empire with at most 60k in their field armies at the time, and forced them to give up the lands being contested in order to avoid a total collapse on other active fronts?

20,000 men is a huge loss on its own and even 10k could have been enough to cost the romans their ability to contest the Muslim armies in the field for years

You don’t need to push the numbers even close to 50k to explain the consequences unless you need to make it seem like a god sent victory/defeat because you are a religion in your infancy and rely heavily on motivated converts