Kalle is right, you can "confirm" a command, but there is no way to correct it. To be fair, regardless of your accent, 15 and 50 sound pretty much the same and on the phone I can never tell what people are saying and I make them say either "five oh" or "one five". The best way to avoid getting 15 if you don't use it is to remove it from the list. If you are using a range of values for the payload such as 0-100 then you can't just remove the 15 from the options, but in these cases I usually use a payload list instead with values 0,10,20,30,40,50,60,70,80,90,100
alternatively you could use a range 0-10 and then just add a 0 in the action parameter like this: setvolume {1}0
since VC uses the Microsoft speech engine you can try training the engine in word using (WSR) Windows built in Speech Recognition. In this mode you can say "correct that" and tell it what you really mean when it gets things wrong. I don't personally think it is worth the effort though, and in the case of 15-50 I don't think it'll make any difference. Often the best solution is to adapt our phrases to avoid ambiguity. In this case you could create a special command with the phrase "set volume moderate" and hard wire that to 50 (i.e. not use a payload).
It is worth doing a couple of WSR training sessions though.
