Hi michaelvv,
Thanks for posting about this. Strava relies on GPS data when recording cycling activities to determine whether or not you are moving. Erroneous GPS data can cause Strava to think that you are moving when you aren't.
Assuming GPS data is complete and accurate, it's still expected to see some discrepancies since different platforms and devices use different methods for calculating moving time.
Strava will use the recorded GPS data when uploading rides to calculate our version of your moving time. During the upload process, whether you recorded with our mobile app or a third-party device, Strava relies on a speed threshold to determine whether or not you are resting. Your device or platform may use a different method than Strava when calculating your stats. For example, consider the process of determining how much resting vs. moving time is in an activity. What constitutes a rest? Is it when you're at rest for 1, 3, 10, or 20 seconds? And what does your speed have to fall below for you to be considered at rest?
I hope this information in helpful.