It’s been a while since I’ve looked at the details of the program I wrote so my recollection of how I did things may be a little off.
The 2 commands you note are functionally different.
12. Manual Station Run (previously manual override) [Keyword /cm]
Turns a single specified station On or Off. Based on your description of what you want to do, I would use this command.
18. Start Run-Once Program [Keyword /cr]
Will execute the program described in the list. If the program described only lists the time for a single station, it will run that single station. In that regard it is functionally similar in result to 12, but you have build a list of zones. I don’t think about it as a way to turn zones off. I’ve not tried it, but I would have thought that it would simply queue zones to run and NOT impact anything that was currently running.
I use 18 when I want to run a set of zones that are not part of an already defined program. E.g. I want to run zones 3, 4, 9 and 10 for 30 minutes because it’s been exceptionally warm and dry and I want to water the 4 sunniest zones. This would be similar to executing 12 4 times, once for each zone.