What is the + and - for on this Triton auto?

[WarpSpeed]

Yes they do when fitted with an exhaust brake or engine brake / jake brake.

Higher compression does not make much difference in light diesels like the Triton because without a Jake brake, the compressed charge acts like a spring on the expansion stroke.

The engine braking effect with light diesels is mostly from pumping losses.

This.....

^Some modern, SUV's or pickups do have an internal Jake brake of sorts built in that there is an auto restrict feature just for that purpose since most are used for or at least equipped for towing and hauling loads etc. Possibly yours is one of those? It activates automatically on throttle release, in a load situation or going down hill you'd notice it more then on regular flat roads..