Some big time bettors will bet on the team they don't think will cover to get the line to move in the opposite direction of what they're thinking. Then they'll bet much bigger amounts on the spread later on.

So if you thought VT would win by less than 10 or lose vs NCSU, you might bet on VT to get the line moved to 11. Then you could bet huge sums on NC State +11. Now instead of only winning your NC State bet if VT wins by 9 or less, you can also win if VT wins by 10 or less, giving more wiggle room to still win the bet