This bolt resides on the right hand side of the block at the back, beneath the right head and just above the inspection port. Once you remove the rear cover you can see it more clearly:
Unscrewed:
As you can see, there’s an O-ring above the flange – and the flange will stop the bolt from being undone far enough for the O-ring to be changed, so if you have oil leaking out past the bolt head you’re going to need to take the rear cover off to change the O-ring.
Someone did once ask how many threads there were on this bolt – looks like eleven to my eyes. This is not how many rotations to loosen it when adjusting the tension – 1.5 to 2 turns out is more than enough.