The Stryd pod can not sense the Treadmill Incline. This is why it is necessary to input the treadmill incline into the Apple Watch while you are running. Make sure you are recording your activities with the Stryd Apple Watch app. This will adjust the reported power appropriately and factor in the incline and elevation gain. (Garmin indoor mode will not factor in the elevation gain)
Open up the Stryd app on your Apple watch. Select the Indoor Run option.
Start your run. While recording your run, scroll down through all your data screens. On the last screen before the music screen, you will find the treadmill incline settings.
Once you adjust the incline, you can scroll back to your other run screens.
Any time you adjust the incline on the treadmill, be sure to adjust the incline in the Apple Watch app!