I would think that would be determined by the spec of whats going in the hole (screw?) and thickness of material. Our company has a guide designers use to determine what the range of the countersunk hole should be and min. material thickness for screws & rivets.
ASME often points to putting things in "alphanumeric" order. A new guy states the number as whole has precident over the value of each charater. e.g.
Z...
NAS1143...
NAS603...
MS21042...
A...
Since 1143>603 NAS1143 is higher on the list. I've never heard this in the military or...
There's a lot of dissention in my office as to how details should be called out. The only guide I've seen in ASME is the illustration shown on the left of the attached file. Usually we do it as shown on the right. We're constantly changing the line type (phantom, hidden), thickness, font...