Driving Belt Torque?!

[SubaSteevo]

Just went to NAPA to get a new ps/driving belt because my old one was starting to crack and made squeaks when just starting. The repair manual says to torque the belt to 143-176 lb using a tension gauge (if I'm reading it correctly)...there's the problem. 1. I don't own a tension gauge, 2. I don't even know what one would look like if I saw it, 3. The guy from NAPA said I didn't NEED TO torque the belt. So I ask you, does a tension gauge exist? what does it look like? do I need it? if so, where can I get one? I'm looking to do the belt today, so any help would be greatly appreciated.

P.S. Could this tension be the torque of the slider bolt that adjusts the belt and not of the belt itself?