By default content within the app is streamed over the internet but you also have the option to make content available for viewing offline. By downloading content onto your device it will take up a certain amount of storage space.
To find out how much space content is taking up on your device do the following:
1. Click the 'Cog' icon below each Channel name (marked 1 below).
2. You will then be presented with the amount of storage space that is being used for that particular channel (marked 2 below). Repeat if you have access to more than one channel.