At what point does the time get used with Time Rate Plan?

Instead of the actual time played, time will be used the same time the video is being buffered.※1
Time will be used in 1 minute increment with Time Rate Plan.
※1Excluding some environments

If I move the seekbar while playing a video, does the amount of time that was moved get used?

Time moved by seeking will not be used and will usage will resume after seeking. However, if you continuously seek in a short period of time, buffer may occur resulting in time use.※1
※1Excluding some environments