When you include default.c it assigns functions to those keys, F2 save the game and and F3 loads the game.

If you press F2 it sets the variable key_lastpressed to 60 and saves this, so when you press F3 it loads its value from the file, thus again showing 60. The ring is beep() being called in the code.

If you want to remove this, either comment out #include <default.c> or in your main function set on_f2 = NULL after waiting 1 frame