Here's an illustration of the flat vs. hill thing from today's ride.

There's not much flat where I live, but hit a several mile stretch- the blurry pic- aved. about 180w,

& a hill for comparison. We powered up a low hill near the end, & got close to 300w for about a minute.

I'm not especially strong but tend to be in the top 1/3 of Strava segments, so don't see how a 300w average is realistic.

The fastest local club/team training ride averages over 20 mph & you see ~ 220w averages.

I know the question was about a 10 mile ride, but still.