Illuminato board with 42 I/O's

@inthebitz

I was looking at the datasheet for the Atmega645 and it shows 53 I/O general purpose I/O lines. It also shows 8 ADC pins.

Is there a reason only 42 I/O pins are being used? Of which only 6 as analog in, instead of 8?

Thanks and loving the work you are doing!