Why is the keydown key code 32 greater than the keyup one?

Question

I made a simple JS fiddle that listens for key down and up events:

window.document.addEventListener('keypress', function(e) {
    e.preventDefault();
    console.log(e);
    return false;
});

window.document.addEventListener('keyup', function(e) {
    e.preventDefault();
    console.log(e);
    return false;
});

When I press down on a letter, the key code logged is 32 greater than the key code logged while pressing up. Why is that?