They only played 14 games a season between 1970, when MNF started, and 1978 when they started playing 16 games.
I only count 661 games.
Then there’s pre-season monday night. Then there’s the season opener that on Thursday that used to be on ABC and was credited as MNF on Thursday. And they used to show playoffs which were MNF on Saturday. And the last few years the opening is a double header. Yeah, this math gets hairy fast.