I want to set a min and max influence range using a driver for the copy rotation constraint. I've tinkered with the driver graph in graph editor but it's too delicate to set my specific range --between 0.499 and 0.97. So when I manipulate the target object in the scene--a slide control bar--up and down, it sets the copy rotation influence between 0.499 and 0.96. The default range is between 0.0 and 1.0 when I slide the control bar targeted by driver.
This is graph editor screenshot with scripted expression from answer. Driver holds influence value at 0.499 but does not increase to 0.96 when targeted slide control is moved along Z axis