I thought of the LCD one, but also that 8 minus 1 is 7 which number bonds with 3 to 10 - though I couldn't quite make that one work. I also messed around with different bases for bit - in binary if you take away a 1 from 3 and add three zeros you get 8 but that seemed even less plausible than the number bond one - in base 4 eight minus 1 is 13 but I thought I was maybe beginning to overthink things at that point.