I was talking NRL

"Mr. J et. al, a general rule of thumb in the NFL is a 1/2 point is worth another 10%"

Obviously depends on the line. Not worth much at all going from 8.5 to 9, but if you can get it on the 3 that's huge. Because not all points are equal there's also some decent EV to be had in selling points.

"Key numbers are where you want to buy the half point (3, 7, 10, and even 14)"

The 3 for 20 cents or less. 7,14 and 17 for 10 cents or less. 10 isn't generally worth it.

For anyone thinking of betting NFL, Sharp Sports Betting by Stanford Wong is a good place to start.