means that the shorter you set this at is the less 'preloading' of data is done when it buffers, that effects how fast it comes back from a buffer.
For example ... If it is set at 8 secs, then theoretically when it buffers it will take up to 8 secs or so much data to be 'pre-loaded' before the picture to come back. That is because it has been told to 'pre-load' 8 seconds of data before picture resumes. If set at 2 seconds , then it loads only that and TV resumes faster, but a buffer may occur again if stream catches up to preloaded data again.
Data amount and time can be confused too. If the data amount is huge and time is less, then the 8 seconds means nothing. The huge data is what counts.
this is all just theoretical really thou, because if the channel or movie loads fast anyway, then that 8 seconds would turn into one. It's that loading meter you see when watching a Kodi addon video, or Ytube has it too. The further away that first bar gets from the colored bar means the 'preloading' data is that far ahead and no possibility of buffer happening, unless them bars catch each other.
And live channels act somewhat different in that most everything depends on the live channel, no matter how you set that buffer rating.
Or vice versa if loading is continuously slow anyway, then a 1 or 2 second setting may take 5 seconds or etc...
To find that sweet spot is the trick. You want 'preloaded' data but do not want so much that it may take longer to achieve that buffer rate where TV starts working again after a buffer.
there are varibles involved other then mentioned too, and is hard to explain correctly for most part... But that generally is what that means, if you follow all that