This is a key point if (like mine) your tool turret can only be moved on one side of the spindle axis. The usual instinct is to touch off external tools on one side of the probe and internal tools (boring bars) on the other. By positioning the probe so that it is offset from the axis in X, you can probe both sides of the tool without needing the turret to go past the spindle centre line. It's worth bearing this in mind when dimensioning and positioning the probe and its support arm.
I have the same type of probe but mine's mounted on a magnetic base and used in the same orientation (ie with the probe axis vertical).