AFAIK, there is no accurate way of knowing free space on tvOS.Bought that one for .99. It seems to conflict with another TV app I bought for .99 as this one reports I have 17GB free and the other one reports I have 16GB free.
That sounds very similar to how it behaves on macOS. 3rd party apps say I am almost out of free disk space. macOS System Info says I have 50% of my disk free.The main reason why is that tvOS can keep a large amount of data cached. This temporary data stays stored on the ATV’s storage until the OS determines that the data needs to be dumped to make room for more data.