Could have cut his wrong like made one side bigger than the other but to him thought it was even and drawing the picture isn't really that hard ( I'm Trying to be rude)
A complementary angle is an angle that adds up to 90 degree each and every time. So, therefore the correct formula to use is 90-63=27. Now, you have your answer and can check it twice if you'd like by the formula. Again your answer is 27.
which applies to a right triangle. I hope that helps you.