Shift, only auto works?

[ufaforwork3]

Shift is a great addition to keyshot. The "estimate vertical shift" button works and make the vertical lines actually vertical. Lets say it puts you at -.14 to be perfectly vertical. Great. But I wanted it to just look less extreme. You'd think you could just cut that in half to -.07? But all that does is shift your whole seen instead of moving what should be the camera back. It doesn't seem to be changing the perspective.

This is also quite useful, but not what I expected for this particular tool. Is there a way to adjust the shift like it does when you hit the estimate button?