My car holds 6 quarts of oil which is 192 ounces, 25% of that amount would be 48 ounces. I ended up putting in 5 quarts of oil and 1 quart of MMO. Could I increase my dosage on the next oil change from 32 ounces of MMO to 48 ounces of MMO.

I would continue to use 1 quart of Marvel Mystery Oil and 5 quarts of your regular motor oil.  Our normal recommendation for the crankcase is to replace between 10 to 25 % of the motor oil with Marvel Mystery Oil.  In your case, this would be between 19.2 ounces to 48 ounces.  However, by using 1 quart, you are making it easier to measure and do not wind up with opened bottles of oil.

I see what you are saying, 25% of 5 quarts would be almost 40 ounces but since I have 32 ounces that should be enough. I will just stick with adding 5 quarts of oil and 1 quart of MMO.