Rude but savvy joke

Timmy is in second grade studying subtraction when the teacher asks, “Timmy, if I have 5 cats and give you 2, how many cats do you have?”

Timmy, “3.”

Teacher, “no Timmy, if I have 5 cats and give you 2, I have 3 left. 5 minus 2 is 3. What if I have 5 cats and give you 3, how many cats do you have?”

Timmy, “4.”

Teacher, “no Timmy, that’s not right. What of I have 5 cats and give you 5 cats, how many cats do you have?”

Timmy, “6.”

Teacher, “that’s not correct, I only gave you 5 cats.”

Timmy, “yes it is, I already have a damn cat.”