I went through this a couple months back. I honestly think the Pentair instructions are in error. They have reasonable numbers, just in the wrong spots, and the plumbing diagram seems wrong to me.
I am running mine so that in bypass the valve sits at about 17. The point is that a small amount of water is always running through the heater to keep it fresh. I started with the valve at 24 (no heater flow) and then backed it off until the back flow valve coming out of the heater open up a bit.
When the the heat is on, the valve moves to 0, so that all the water goes through the heater.
Of course if you are plumbed the other side, the numbers become 24 and 7, rather than 0 and 17. These are the four numbers Pentair uses, but they pair 0,7 and 24,17. This makes zero sense to me. I would not be surprised at all to find out that some engineer wrote down the numbers (after careful and considered testing) and then they got transposed by the person who wrote the document. Having said that, my valve is not plumbed the way Pentair shows it. I don't know how a T Diverter valve can work the way they show - normally I would expect the input (in this case the cold water from the filter) should flow into the center port, and that is they way I have mine plumbed.
This has been running a couple of months now and seems to work well. I have the same cooldown issue that others have reported, but when the valve is in the diverting position, the pump runs significantly less RPMS that when the heater is on/valve is fully diverting. Note that I use constant GPM on my pump so in "neutral" I am always running just enough flow to keep the SWG flow switch open. You can really hear the pump RPMs step up just before the heater comes on.
Dale
