Yes, you could take 4 in one hour if you so chose. 1.3grams of acetaminophen in a single dose might be slightly high, but it's not on the lethal end of the spectrum.
20mg of oxycodone might be a little too much if you're opiate naive. Other than that I see no problem.
This type of question should be posted over in basic drug discussion tho, as it is pretty basic.