I just used GDS2 to see what HPCM2 reports for my battery capacity. Also included are the previous measures I’ve made with GDS2. Degradation seems fairly linear.
07-29-2017, 11000 miles, 18.5kwh
12-03-2017, 16700 miles, 18.1kwh
07-26-2018, 25800 miles, 17.5kwh