Hi there!
As the other person also said: short games are completely fine!
It is actually recommended to create games that are on the shorter side (5-10 minutes max to experience all content), for a few reasons:
1. People rating your game won't be playing the game for hours and hours. If your game has hours of content, the players rating your game won't experience all content which might influence your rating (negatively!).
2. Scope issues... The jam is only a week long, so planning a super long game might result in not being able to do everything in a polished and nice way, which would also negatively influence your ratings.
Jams are a learning experience, where you are free to go out of your comfort zone and try to finish a small project. If that small project is a 2 minute long game, that is still an achievement because you finished something!