IF the product contains the specificed active in the specified dose, that is a lot.
Now alprazolam is one of the more forgiving benzodiazepines but it produces tolerance and dependence just as well as the others.
It's more a question of what you expected 20mg to do. Because while it IS possible to stay awake, it's a very bad idea. The a1 activity produces both retrograde and antiriorgrade amnesia as well as loss of executive control i.e. people will tend to lose all judgement.
I really would just go to bed. You don't want to wake up in a cell with no idea what happened.