It looks like you are afflicted with the mysterious battery capacity 'reset'... Read the section entitled "Odd 'Resets' of Battery Capacity" at the bottom of this page: https://github.com/clarity-phev/Battery-Capacity-Read You could have gotten a reset up to 55 aH at some point, and have mostly recovered toward the 'correct' value. If you had more readings, it may have been clearer as to exactly what happened.
Thanks MrFixIt for this thread, and everyone for the information. Added the first data point from Idaho, although the car spent its life in Los Angeles.