A good way to look at it is;
If you take Nebraska -28, you have to subtract 28 points from Nebraska final score and then see if they still win -or-
If you take S. Miss +28, you add 28 points to S. Miss final score and then see if they would win.
If you were betting in Vegas (or elsewhere), you bet $110 to win $100 so, if you lose, it costs you $110, and if you win you get $100. The spare $10 is considered the "juice".
Sorry, used to be "involved" in the industry back in my college days.
Wow, complicated. I just think the Huskers win, lol.