The lowest cone value should be first in the direction they lean. I always put the flat side toward the direction they will sag. I think this is the way recommended...pretty much like the picture. I never have used a protractor to measure angle. I just make sure that they are slightly bent towards the direction I want them to sag. if you wish to be more precise, that's fine. I like to fire my pieces to the point the middle cone ( the range you are looking for) touches down. Of course there should be three cones, one above and one below the cone you are shooting for. I leave just enough room for my cones not to hit each other when they sag. The lower ones should be pretty much down before the next one sags, so they can be within a cones width of each other. You want to be able to see them all through the peep hole.
Remember, firing a kiln load of ware is not something that can be absolutely reproduced from one firing to the other. As an old time potter I feel more comfortable seeing the middle cone down and the next higher just bent at the end of a run, but as has been mentioned many times, total heat work is what determines the glaze results on any run.
I have half a cone difference between the top and bottom of the kiln and it makes little difference for the glazes I use.
WRITE EVERYTHING DOWN! When a kiln load turns out right, try and reproduce conditions as much as you can and don't get to caught up in the some rigid set of "must do".