"How short does this need to be?"
"Well... shorter than before obviously, but not too short"
"What is too short?"
"When you have too much room left over, then it is too short!"
"How much room do we have?"
"Not enough to go around, so it needs to be just right and not too short, but we can't have it go over either."
"What happens if it goes over?"
"Then it will short the excess on the other margins... it can't go over, make it a little short but try not to leave too much room... Oh for crying out loud, let me look... no, that is way too short!"
"So I have too much room?"
"You will, if you leave it that short, make it longer."
"How much longer?"
"Almost twice as long, maybe a little shorter."
"What are the margins for?"
"Sigh... In case something goes too long it will provide a little slack."
"So I need to make this a little shy of, twice as long?"
"Yeah, and don't go over, it will make our margins to short and we won't have enough slack for other mistakes."
"Okay... a little short of twice as long as it is, because now, it is way too short."