Thanks I can't duplicate that what which is why it was not clear. From yours I see these parameters
&time_t=67200&duration=300
From mine with CoreElec and Windows I see the expected time.
&time_t=1629230397&duration=3600
Those parameters come from Kodi core so the addon doesn't really get involved. It is not exactly clear why NextPVR is even creating this recording for you since it should generate a recording service not running error. It would be interesting to see your NextPVR logs.