This is a case of knowing enough to be dangerous 8)
The 44 & 43 are the physical pins of the ATMega chip itself.
Following the leads to the right, they end at header connector, where they are marked D20 & D21.
There is software mapping that goes on in the IDE (in the pins_arduino.h file) so when you toggle Port D pin 1 & 0, the result shows up at header pins D20 & 21.