[Imp]

This game is actually very good at explaining what things actually do unlike most modern games that are rubbish & give you no idea how the mechanics work.
It does not & should not give exact details you know the higher the rangefinder for example the better. Judging the difference between 6 & 22 is down to you, as are all the other factors that apply.

Same goes with this you know 0.4 is not going to drop many shells so your decision is fire this turn or adjust it so you get 1.0 or 1.1 & fire next turn.

If your targets dug in you might well go for the 0.4 as it allows you to adjust next turn & the target is unlikely to run.

If its mobile say SP Artillery in open ground delaying for a bigger fire mission in the hopes of a kill makes more sense as it will probably run if it survives the 0.4.

Cannot see any reason you need to know more about the delay procedure.

To help out in this decision smaller normally have a higher ROF than larger so firing something like a 60mm mortar at 0.4 is more worthwhile than firing 155mm at 0.4. Larger than that you will be lucky if it fires more than 1 shot at 0.4
The only other part of the decision making with artillery is your objective suppress (high ROF) or damage unit or terrain (high Kill or Pen depending on target type)

It does not take long to determine how the different mechanics combine no need to count the shells I never have.