I got the same notice and mine reads:
" The main drive litium-ion battery on your 2012 i-MiEV is covered for defects in material and workmanship for 8 years or 100,000 mile, whichever comes first. In the event the main drive lithium-ion battery cannot be charged to full available capacity when properly connected to a properly functioning compatible charger, however, Mitsubishi is extending the warranty on the main drive lithium ion battery to 10 years or 100,000 mile, whichever comes first.
...
This warranty extension does not apply to gradual capacity loss based on time and usage. The capacity of the main drive lithium-ion battery, like other commonly used li-ion batteries, will decrease according to time and usage. This type of decrease in battery capacity is normal. ..."
This just means, that we are worth off with a MiEV then the Leaf-owners, they have a definite capacity loss to refer to.
BTW, one of the reasons, that I read this so negatively is:
I had the 36,000mi battery check done and they re-calibrated the battery. End result is, that I had regularly 80+ miles(May/June 2015) before and I checked it to/from work and have now low 70th (Mid Sept.).
I don't know, what they did but it stinks. I would not recommend to anyone to get this done, unless there is a need to get the warranty to stick.
Regards,