The volume is equivalent to a 9" pie pan and designed so you can use a standard filling recipe. However, this pan has a larger outside surface area than a round pan; for a crumb style crust (Graham cracker, Oreo, etc.) you need to increase the recipe by about 25%.
For a pastry crust you can increase the recipe if you want, or just roll the dough a bit thinner. When using store bought pie dough my partner Chris just rolled it to an oval shape 3-4 inches wider in one direction (he wanted to say 10x13" or so but wasn't positive).