When looking at the Battery Report utility, you will see that there is a difference in the battery design capacity versus the full charge capacity shown.
(Figure.1 XPS Battery Report)
Cause information is not available.
This disparity can lead people to falsely assume that there is a problem with their laptop battery.
Full Charge Capacity: This is affected by several factors that are constantly changing. (For example, changes in the external temperature, ambient temperature, system heat soak temperature, along with things such as the number of discharges to 0% and the number of full charge cycles.)
Design Capacity: Has a 10% buffer to allow for external changes during use. (For example, system heat can cause a cell to overvolt ever so slightly.) This prevents the battery from spiking and causing damage to the life of the battery cells.
This is standard industry design and practice and the battery is working as designed.