I may have not read everything fully, but I don't recall seeing any time limits for the game, like how long or not long it can be. 

There are no limits to the length of the game. You can make a game as long, or as short, as you would like it

There is no rule regarding length/time to complete, but if you are competing I would suggest aiming for 7.5k-10k with a complete story. 

The judges are looking for reasonably short but complete experiences.