GPIO pin assignments

I am working with a nanopi neo.  The overlay documentation says the default pps pin is PD14.  How do I cross reference the gpio names in the overlay documentation to what the documentation on friendlyelec site.  I dont see anything close to a PD14.  None of the pin assignments match whats in the manufactures documentation.  The I2C pins and a few others are clearly marked from the manufacture, so I could give that a good guess.   Other than that, where do I find or how do I figure out which pin does what?

Rob