This behavior is controlled in VBAdmin by the SetSigDgits command. You must have this currently set to "1".
********** ISN Voice Browser Configuration Utility ************
>>>>setsigdigits /?
The number of leading significant digits (not including the tech-prefix, if it exists) which ISN will strip from the incoming DNIS. The value that is stripped is saved and prepended with a # sign to any transfers which occur out of the ISN Voice browser.
Valid Values: an integer >= 0
Default: 0