I graduated with an English Degree, Math is not my strong suite. Just looking for some help determining how much a pointspread is off for the game when the 2nd half line comes out. Probably simple stuff for most of you but I am having trouble figuring out when a favorite becomes a dog per the 2nd half line.

Example- A -4 favorite is losing by 10 at the half. 2nd half line has them at -3. SO for the game they have gone from a -4 favorite to a +7 dog. Now what percentage has the line changed from the original line? I have been unsure whether or not my math was right for faves that cross over into dogs.

Also, when trying to figure out how much an O/U line is off do you simply take (1st half score + 2nd half O/U line) - the original O/U and then divide by the original O/U? Is that an accurate line to see how far the original game line is off?

Again sorry if this is rudimentary stuff but I am not a math guy. Appreciate any help.