According to this
http://www.boone-crockett.org/bgReco...Whitetail+Deer
"Circumferences are taken at the narrowest place as detailed in Figure C for each measurement. If the brow point is missing, take H-1 and H-2 at the smallest place between the burr and the G-2 point. If the G-4 point is missing, take H-4 halfway between the G-3 point and the tip of the main beam."
You have to take 4 circumference measurements on each beam.
The circumference measurements are:
LH1 4 6/8
LH2 4 2/8
LH3 5 5/8
LH4 3 5/8
RH1 4 6/8
RH2 4 2/8
RH3 4 4/8 (halfway point)
RH4 4 4/8