Interupt pinouts don't seem to match on Mega2560 data

I have been looking at the interrupt pin outs, into, int1... on this page, ATmega2560-Arduino Pin Mapping , and the data from the reference page for AttachInterrupt(), . The interrupt descriptions on one page do not match the other. int0 on the pin outs page is digital pin 21, and int1 is digital pin 20, etc. The information on the reference page AttachInterrups(), int0 is digital pin 2, and int1 is digital pin 3. It is very confusing. Is it meant to be this way, or is this an error?