Take a close look in that pot-you may have 4 or 5 little plants, not one.
Pull them apart and give each plant a gallon size pot. If you have just one plant (can't tell from the photo), then that's a good size plant for grocery store mini!
I let mine grow outside in the gallon pots for a few months, then I plant them in the ground and they do just fine.
A few years ago, Trader Joes had minis 3/$10, so I bought 3 and ended up with 12 plants. I made a mini hedgerow! That one was a bright red and white stripe, possibly 'Charlie Brown'. This spring, I bought the same one you have pictured, a dark ruby and white. It's still growing in my kitchen window, but it will go outside soon. Does anyone know the name of that one?