I bought one a few months ago at the request of a client; it was to go on the top of a cupcake display. Because I make cake batter in such huge quantities, I can’t tell you how many cups went into each side; I eyeballed it.
The bottom part took a long time to bake through (because it is tall, think a 6” round by 4” deep pan and you’re on the right track) while the swirl part baked quickly and was done faster than the deep end of the pool It probably would have been better to not fill it half way and the baking time might have evened out better.
You sandwich the two part together with icing and then decorate. You could also coat the bottom with piping gel and cover it with fondant to mimic a cupcake liner (turn it upside down then right side up when finished) and I think that would have been better than trying to use icing.
All in all, I wasn’t crazy about it; I think it was a waste of money and probably won’t use it again.