you mean in iOS or on the web? For web, the Study page has bars with your progress, and if you hover your mouse on the bar, it will show how many you have remaining... same data if you click on the lists.

for iOS, you can see it on the "My Lists" part of "Lists" link on the main page. [however, this one's usually out of date unless you explicitly click the refresh button].

If you want to see it WHILE you're studying, that's not possible, and I don't think it's really practical to implement.