Have you read the documentation on tokens?
Press F1 while VoiceAttack has focus to open VoiceAttackHelp.pdf in your default PDF viewer, which contains information on VoiceAttack's features.
This topic may also be of use, in addition to the official documentation:
Variables and tokens summed upTokens are text, so if you use the appropriate token for each of your variables to retrieve their value, you can put them one after the other, followed by the zeroes you need, and then set your decimal value directly using the "Set a Decimal Value" action's "Convert Text/Token" option.