Apparently this has to do with an older version of the EN-EL15 battery that comes bundled with other Nikon products or sold separately. It seems that the battery can cause the camera to display the wrong number of maximum shots possible. The good news is that Nikon has announced that they will be offering D500 owners a free battery exchange for the newer model.
According to Nikon, “The later version of the EN-EL15 batteries supplied with the Nikon D500 have been tested in accordance with CIPA standards, and do support the maximum number of shots possible (battery life) indicated in brochures and other documentation. However, when some EN-EL15 batteries, either purchased separately or supplied with another model of camera, are used with the D500, those batteries may not be capable of the maximum number of shots possible (battery life) indicated in D500 documentation.”
Basically if you are using the battery supplied with the D500, you should be good. If you are using an older battery from another model or if you purchased it separately, you could be affected by this. If you’d like to get your battery exchanged, head to Nikon’s website for the details.