Rethinking Smoke

[Juiceman]

Not sure I want to wade into this fire fight since I am late to the party....  

From the 4th Edition Rules Page 50:
 
Smoke and Illumination (4[sup]th[/sup] Rules Edition Page 50)
Unless forbidden by scenario special rules, all mortars, on-board artillery units and off-board artillery increments conducting bombardment attacks have a limited ability to fire smoke or illumination rounds instead of causing damage. A unit or off-board artillery increment firing smoke or illumination may not also conduct Bombardment or Direct fire in the same turn (place a Moved/Fired marker on it, or make a note if it's an off-board artillery increment).
 
This paragraph to me means that each individual “on board BF unit” and any “OBA increment” can fire either a smoke or illumination round instead of BF during its activation or turn. (I added the bold & underline).
 
Limited Ammunition (4[sup]th[/sup] Rules Edition Page 50)
Each side in a scenario has a number of turns of smoke equal to 10 percent of the turns in the game, with fractions rounded up. So a 12-turn game allows for two rounds of smoke/illumination, while a 36- turn game would allow four turns. To track usage, place either a Smoke or Illumination marker under the firing unit to indicate one usage, or note off board artillery's usage on a piece of paper.
 
Why would you have to mark the individual firing unit(s) unless it is rounds per “on board BF unit” or “OBA increment?”  Each unit has a certain number of turns or activations to fire either smoke or illumination rounds instead of your typical BF. 
 
Using the example from above of a 12 turn game, if your side has two 81mm mortars and 2 16 point OBA increments you have the potential (see below) to fire smoke or illumination rounds twice per game per unit but it is not guaranteed.
 
Question: If on the other hand it is by the turn does that mean that all of your artillery assets, both on & off, are firing smoke or illumination rounds that turn and if so how many smoke or illumination counters do you get to place on the map? Only one or up to four? What about the dice roll below, does that negate one round or four rounds. 
If played this way would make the optional rule very gray, almost black.
 
Procedure
For each unit or artillery increment firing, the active player designates a spotted target hex within range and rolls two dice. On a result of 5 or more the firing player places either a Smoke marker or an Illumination marker in the target hex.

I see it as turns of smoke/ illumination rounds per unit or increment per game provided you roll 5 or more to place or you lose the round.