Garmin versus Xert power number

Why does Xert always have lower max power numbers than Garmin when my power numbers are fed from my SRM to my Garmin and then Garmin to Xert?

Also, if your Garmin is set to ignore zero power numbers when not pedalling, will the Xert file do the same? If your Garmin is set to turn on at 10kph and auto off if less than 10kph, what data will show in Xert? Trying to understand the differences between average and normalized power between the Garmin and Xert.

I don’t believe that Xert ignores zeros. I recently went on a 100km ride with a friend who was somewhat slower. Everytime we had to switch from one road to the next, I would stop, and wait for him to catch up (so there is no chance of him getting lost). When stopping, I would pause the garmin 520 ride recording. Garmin connect recording dutifully ignore all the stops and showed me only the riding time in its analysis. Xert including the breaks, thus drastically dropping my avg power.

Both MPA and Difficulty Score are affected by rest so Xert included them. Are you reviewing the Activities Table when comparing your max power numbers? (Add Max Power as a column to see the value for an activity).