Hi Koerky,

As you already know, streaming video takes a bit more bandwidth than streaming music or browsing the web. And even if you do set the app to stream at the lowest quality, some of the videos are pretty lengthy, so that might have been it too. But using nearly 700mb at the lowest quality in less than 30 minutes sounds strange.

I would check if the app specifically used that much data or if it was a collective app data usage from all of your running apps in the background.