This is a question we get ALL the time... In fact, it's come up twice in my inbox over the last 2 days:
"How is a total of -11 (-1 Dallas and -10 Green Bay) passing yards figured in the Oct 24, 1965 game when Individual stats show Craig Morton for 61 yards and Bart Starr for 42 yards?"
"This query should return this game [...] Elvis Grbac threw for 504 yards, and the Raiders scored 49 points. That game was not returned by the query[.]"
In both cases, it's a question of individual passing totals seemingly not matching up to team totals. And that's because the NFL doesn't define "passing yards" in the same way for teams as it does for individuals.
Confusingly, sack yards do not count against the "passing yards" you see listed next to individual players, but they do count against "passing yards" at the team level. To put it another way, individual passing yards are always presented as GROSS yards (with sack yards not subtracted out), while team passing yards are always presented as NET yards (meaning sack yards are subtracted out).
So despite Morton & Starr's combined GROSS pass yards, there were also 114 combined sack yards in that game, leading to a record -11 total combined NET passing yards in the game. And despite Grbac's 504 GROSS pass yards, he was sacked 4 times for 30 yards, meaning KC only had 474 NET passing yards in the game.
This probably doesn't make a great deal of sense in 2013, but it does come in handy for years before QB sack data was tracked (a.k.a. the history of football up until 1969). Because of this practice, we know how many gross yards a quarterback -- and, therefore, a team -- had, as well as how many net yards they had, since sack totals were recorded for teams (but not players) before 1969. It would make for even more confusion if, starting in 1969, we all of a sudden began defining yardage for individuals differently than it had been defined in the past (though as we saw yesterday, this didn't stop the NBA from abruptly changing how team rebound totals were defined).
So it's a minor inconvenience now, but probably a necessary one from an historical perspective. And hopefully this post will reduce some of the confusion going forward (though I doubt it).