The manual is not very clear on how to check the chain tension. I mean, at first glance this doesn’t look obvious:
To use this procedure you need the rear lifted from the ground, but from the swing arm with your favorite lifting gear. Not with a center stand…
Then with the top portion of the chain taunt to begin with, you lift the lower chain in the position they indicate at the rear end of the B arrows, flattening it out. The gap (‘A’) needs to be 2-5mm (source).
There is another view of the same method, this one documented on a sticker affixed to the swingarm:
If in doubt prefer a loose chain. At rest on the side stand, the chain should be very slack.