ok.. the basics.
XC is more of a TEAM sport than an individual sport.. Although you have an individual winner and usually a top 10, 15, or top 20 awards, it is still a team sport.
It is scored by places, in other words, if your top 5 runners finish in 1st, 4th, 7th, 10th, and 15th place, you score 37 points. The team with the lowest score wins. So it really doesn't matter if you win by 1 second or 30 seconds, your value to the team is still only 1 point.