Gabe,
Mint goes crazy wild. Period. It takes off in the garden if left to run wild. The pot contains the size. You can divide it, and it'll fill the pot. Take it out, take a hold and pull left to right. You'll have two plants. Both will fill the same size pot you have. You can also leave it be. It won't suffer. Water it, and you can give it a little feed if you like, but as the soil looks to be rich, and new, likely no need.
