I’ve come up with the perfect explanation for how I would estimate stories.
First, we are not measuring time or complexity—we’re measuring effort.
For this example forget all you know—or think you know. Let’s ignore everything about T-shirt sizes or hours… instead we’ll think about vicious canines and the effort it requires you to render them unconscious in order to stop an attack.
Incapacitating a chiwawa (not Phil’s, I’m sure they’re nice and not vicious and we don’t want to hurt them) doesn’t require much effort at all. You have no fear to simply bend down pick it up and (as gently as possible) toss it a few feet away—out cold.
Incapacitating a mastiff (you initially thought was a horse), however, requires a significantly larger about of effort. I don’t want one of those sicked on me. You may resort to running, kicking, or beating him with a stick…it still may be attacking you.
Who is providing the effort makes a difference. If Dave, significantly stronger than I am, was knocking out the mastiff, he would perform an elegant taekwondo chop to the poor beasts skull and the attack would be over and out cold. Me, even if I used the biggest stick I could carry, it would still take significantly longer to render the dog unconscious.
The actual effort required to halt the attack is the same in each case for each of us, the dog needs to be knocked out—same problem same amount of effort.
The chiwawa is the story that requires the least amount of effort we have. The mastiff swallowed several chiwawas he thought were burritos—an epic with a LOT of effort.