I never trust the manual's chain tension rec's on any bike, but that's just me.
My "right" way involves some work the first time around. Pull the bottom pin from your shock and move it out of the way. Jack up your wheel until the chain is at its tightest point (roughly horizontal). Adjust the chain just to the point where it doesn't bind at the longest point in its arc.
Put the shock pin back in and sit the bike on its kickstand, then measure the slack. That will forever be your minimum slack measurement with the bike on the kickstand, and you'll never need to worry about it again. If you ever change rear sprocket ratios take the time to do this again, as the measurement will change a bit.
After doin this measure the chain slack from the TOP of the LOWER run of chain to the bottom of the swingarm, from a measuring point that you will use consistently. Much easier to eyeball than the wigwag method in the field.