It's pretty common. Teams sometimes get blown out for whatever reason that isn't necessarily representative, so it caps the damage of one bad game.Here is a sentence from NCAA’s website concerning scoring margin to confirm my earlier statement-
“So, too, is the winning percentage, the adjusted winning percentage (based on where the game is played — home, neutral or road) and the scoring margin with a cap at 10 per game.”
They cap at 10 pts.