I wouldn't count anything by someone who used scripting to get around the length. Then it's really a contest for who can game the system most efficiently, not who can write a good story in a short space.
The length formula is secret, but like ogre says, 1 would be incredibly short.
Just checking my own stories:
Snow, hell girl, and desperate heart are all 4, and haunted is actually a 5, and I'd consider all of those short.
Erika bakes a cake, which was for the 90 min contest, is still a 4.
Kingmaker is a 3, and it's not actually a story, plus it only has about 2 sentences per page.
Even High school romance, which is terrible and only about 5 pages long, still gets a 2 for length.
In my totally non-scientific study of only stories I wrote myself XD, it seems like 4 is the spot for "still a very short story but capable of being good."
So I suppose if I were making a contest, I'd set it at 3 and below. No scripting. XD