I'm honestly not sure; I don't remember how many quarts/gallons it was displayed at. It's the biggest one Walmart sells when it's not Christmas-time, and it's about 3 feet by around 18 inches by 18 tall or so. I don't have a ruler to measure exactly so that's all from eyeballing it.
And it is indeed spaghum moss in that lil container! Spazhime recommended it on their tumblr, and while I haven't really seen Maze use it, I'd prefer to give her the option. She hasn't figured out that she can dig yet, but that might just be a side effect of not having a super thick layer of substrate right now (I didn't sterilize enough this time around, my bad!!)