Type in your number. Press space once you are finished. Press space to see if you want to multiply, divide, add, or subtract. Click the symbol once you are done. Type in your second number. Press space for an answer. Press space again for another calculation. Just know that any digits that go off the screen will be deleted, just to keep lag from coming if the number has lots of digits.
This is a bad project. Do not, under ANY circumstances heart or favorite it. Under 500 blocks for this entire complicated project! Noice.