Submitted my diagnostics - recorded 60 minute Sportscenter displays on Shield Android client as 815 minutes.
I checked the back end and it does appear that it actually did record for this length of time:
TV/SportsCenter With Scott Van Pelt/SportsCenter With Scott Van Pelt 2017-02-06 2018-05-01-0359.mpg
Duration
13 hrs 36 min
Bit Rate
473,156 bits/sec
File Size
2,893,766,876 bytes
Track #0: H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
1280x720 16:9 yuv420p progressive
Track #1: ATSC A/52A (AC-3)
5.1(side) eng 384kbps
Track #2: ATSC A/52A (AC-3)
stereo eng 192kbps