Gertboard ATmega IO vs. Arduino Pins
The printing on the Gertboard indicated the port and pin numbers internal to the Atmega microcontroller…
However this is normally hidden from the user by the Arduino’s “wiring” library and rather than refer to (e.g.) Port B, bit 5, you’d normally refer to “pin 15″.
The mapping is fairly straightforward, but to help you connect wires to pins on the Gertboard, here is a handy table to let you see what the connections are: