Hello.
You can go with the dictionary definition of asymmetry: lack of equality between parts or aspects of something; lack of symmetry.
Wikipedia has an illustration that explains the same concept visually:
In the most basic way, you can draw the sprites or models of your game with one half a different shape than the other half, like the tree on the right in the above image. Just with that, your game already follows the theme in the art department, that’s why they mean with “art-wise”, and that’s enough, if you want.
Following the theme narrative-wise would mean that your game’s narrative—that is, one or more of the plot, characters, or lore aspects described in the jam‘s overview—also has anything to do with asymmetry. For example, you can make a game in a world where everything is symmetric and the protagonist is looking for a different way—a “quest for asymmetry”, if you will. Another, way more sensitive, example would be a game about a woman that recently has gone through a mastectomy and has to learn to live with it.
You do not have to stick to the dictionary definition and can be creative with the theme. For instance, you can have a kingdom called “Asymmetry” that is constantly in war with the neighbor kingdom, called, of course “Symmetry”. Or you can make some kind of letters game where players must spell the word “Asymmetry”. Or any of the thousands creative ways you can imagine of interpreting the theme.
In short, as long as you can justify, as it were, that “asymmetry” is part of your game, you will be fine. People will rate according to how much they agree with your interpretation, but i do not think your game would be disqualified.
I hope this helps.