I've noted that the Design Capacity indicator changes on my battery. I understand that the full charge capacity would decline of the life of the battery and the relative difference between full charge and design capacity would be an indicator of the health of the battery.
As refrenced in several forum discussions, other members with systems that support dual mode batteries - maximum run time or maximum battery life span modes, have noticed changes in the reported battery design capacity.
Power Manager is doing this, not the battery. It is reporting the charge capacity as being the same as the level it is stopping the charging at unless you disable the adaptive threshold. The charge capacity will go back to the design capacity after changing the setting and either going through a charge cycle or recalibrating it
Power Manager may cause this change if it has been changing between Maximum lifespan mode and Maximum runtime mode ( which does in fact trigger the battery firmware to report a different design capacity). This is explained (somewhat) in the Power Manager help file.
In Advanced mode, battery tab, click on the "battery maintenance" button. Under "charge mode" there's a "learn more" link which will open the help file to the page about this topic.
Note that performing a battery gauge reset while in "automatically optimize" mode may reset the battery to maximum runtime mode until Power Manager changes you back into Maximum lifespan mode based on your usage.