gunnery officer had to have complete control of his gun crew and guns during battle. In a convoy
you could shoot each other up and also friendly aircraft. At times the big guns were ordered not to fire and the 20mms could. Or certain 20mms could. (This is just one example.) My guess would be if you had a 20mm on the bow it would be the #1 20mm. If the odd numbers stayed starboard it would just make the numbers higher as you went aft but using the same system. Some of the troop ships had extra 20mms plus other guns and you would think it would be easier to remember during battle starboard odd, port even. I can't answer for sure. Except for Roy's 20mm
position and my 20mm assignment on different ships, his forward starboard bridge, mine aft starboard bridge, both odd numbers.