ex. today Den favored by 5 1/2 at Ind.
This system is not a secret and some books like Betus inflate the lines to make it harder to win the wager.
If this game were a "C" game, the line might jump to 7 or 7 1/2.
This way buying the points you would be in the same position you would be with "normal" lines. They would try to sway you from the wager especially with all you would have to put up to properly cover your chase system wager. And it works because many times I for one have "chckened out" of full 'C" wager for fear of losing it.
This is my interpretation. Some may agree, others may differ which is fine.
Best of Luck