What does the fourth number in the FW version mean?

[Ondrashek06]

Switchident says that my Switch's firmware is 16.2.0-10. What does the "-10" mean? It used to mean the eShop version back on the 3DS, but now the eShop is basically a webpage so it has no relations to firmware updates.

 

[linuxares]

Im not 100 on the Switch but most of the time its like a debug code. Like a more unique identifier than 10.1.14