Mine has had far worse
Mine has had far worse degradation with a loss of 22.5% at 97,000 miles and that is with me doing everything in my power to trickle charge past 80% or never crossing 80% charge. Additionally charging at night in San Diego during perfect temperatures should have allowed for additional reduction in loss for the battery and temperature systems.
I have to add a side note that I am sure i have one failed cell in my batter pack that GM never acknowledged and since I have had to point out every issue with this car tell them how to fix it 5hen they finally do it. I have never had confidence after mile 10,000 on this car. I. Addition to that i have a rear suspension issue that has been going on for 80,000 miles which they refuse to fix because their technicians are deaf.
These batteries have always been an issue unfortunately one i did not understand till after 10,000 miles.
This is .y personal experience.