Do the pedals still need to be properly torque wrenched on or you can get misleading data? The Garmin forum may also have more info on power imbalance and even the multi step installation procedures.
How were your muscles before/during the ride you got the data on? Muscle fibers in one leg that are tight and shortened may be unable to produce equal power to the other leg. That’s one reason on long hard rides I stretch quads, hamstrings and glutes during the ride to keep muscle length-tension. Could you sense if you were pushing and pulling on the pedals equally with each leg?
At least you may have gotten a warning that something may be going on so you can take measures to improve the balance in your pedaling biomechanics.
You may want to pm Wahine about it, especially the leg length difference.
‘The negative feelings we all have can be addictive…just as the positive…it’s up to
us to decide which ones we want to choose and feed”… Pema Chodron