It's an important reminder that miles remaining is sort of a worthless number. Switch to percentage and leave the miles estimates to the built-in nav. Calculate miles from your percentage as outlined on Bobby's site.
Not degradation. The range estimator is not accurate, if you leave your car plugged in, let's say at 80%.... In a week or so, the range estimator would show me 20 miles less even though I'm at 80% still.
Its simply not accurate and I think it won't show properly until you do a full 0-100% charge cycle. So best piece of advice is to IGNORE IT and to change your display to % only.