Trying to do my own maths to understand glucose levels

I have 2 questions related to glucose just after having a meal.

Assuming we have 5L of blood. If I get a meal containing 50g of carbs that makes a rise of 10g/L = 1000 mg/dL. This number is way too high so what phenomenon makes my maths incorrect ?

Also we see everywhere the normal glucose levels 2hrs or 4hrs after a meal. What about 5 min after a meal? Can it reach let's say 500 mg/dL ?