Sorry, i'm typing over you. See how you go. So 10* is degrees, ok im a bit thick tonight--or most nights.
I guess ya trying to line up a casting mark which i dare say is how the book says but i just fly blind--damn near blind anyway--if all else fails then read the instructions!!.
It'll still lift the clutch no matter where it ends up so long as the cable free play is adjusted out.
Factory casting mark is the optimum point for best lift.
Where did all this start--no clutch etc?--maybe i missed it earlier in your posts. Cheers.
ps, i'm forgetting you're reading a manual.

I see now looking back you mention clutch drag & that's most likely cause by something other than adjustment. Favorite thing to remove is the 5 or so rubber or plastic rings if still in place as can sometimes cause drag. They sit inder each original fiber plate. Are the fiber plates all good & none broken. 

I have two DT360As and went thru the exact same thing you are describing regarding that 10 degree specification for the pivot arm. I never could obtain it. I gave up on it and simply adjusted the clutch as Morley described.

So the clutch push rod should be in contact with the pivoting arm and any free play is at the clutch hand lever?

Well--not realy but don't worry, its a combo of both.if you have a nice new free moving cable & a little bit of free play at the handlebar lever, the curly spring on the arm under the motor will pull the arm back giving a little clearance on the pushrod which is what you want. Don't panic. If for instance you had zero free play on the handlebar lever or going to the extreme & had minus zero "tight lever" then there's pressure on the pushrod constantly which would cause the clutch to slip under acceleration but that's going to extremes. You'll be ok. So long as you have 'some' lever clearance at the handlebar you can't go wrong. That's all you need to worry about.

The best advice I can give is that you want the clutch release arm to hit resistance about 15 degrees ahead of perpendicular with the cable. This gives a better clutch feel, a nice break-over at the lever as the cable pulls the arm toward perpendicular at full engagement, where it has maximum leverage. If its just starting to load the release arm at or even past perpendicular, the pull will be difficult at the lever with increasing spring force and decreasing mechanical leverage toward full engagement.

Sometimes the external adjustment is insufficient and you need to get under the side cover and look at the height of the clutch plate stack or the pushrod length.