Tire size plays a huge part.
For instance, for the indicated numbers provided in your picture, you could be running any one of the following setups and obtain the same numbers.
3.21 gears with 23" tires runs at 2757 RPM's at 70 MPH.
3.73 gears with 27" tires runs at 2729 RPM's at 70 MPH.
4.10 gears with 30" tires runs at 2700 RPM's at 70 MPH.
4.56 gears with 33" tires runs at 2730 RPM's at 70 MPH.
4.88 gears with 35" tires runs at 2755 RPM's at 70 MPH.
One other thing to take into account. If the tires are considerably larger than stock, the speed sensor system needs to be recalibrated for the larger size (can be done by the dealer up to a point or can be done with an AEV ProCal or similar programmer).
With the above numbers in mind, I would say that the speed sensor system needs to be calibrated to your tire size as none of the above tire size/gear ratios makes sense (with the exception of maybe 4.88's with 35's) in the world that Jeeps typically operate in.