Have you read the documentation on the features you are attempting to use?
Press F1 while VoiceAttack has focus to open VoiceAttackHelp.pdf in your default PDF viewer, which contains information on said features.
This topic may also be of use, in addition to the official documentation:
Variables and tokens summed upSomething that may not be mentioned explicitly is that converting text that represents a numeric value to an actual numeric value means that text must
only consist of that representation.
E.G. "50" is a convertible representation of a numeric value, "turn up 50 percent" is not.