You need to collect exactly one digit from the Get Digit String; then (assuming one was entered) incrememnt a counter. Then have another Get Digit String step. If that one collects a digit, then you're dealing with an extension (keep collecting digits), otherwise if collectedDigits=1 then it's a menu option and you can determine what to do based on what that digit was.
You can look at the attached example. It does not handle extensions that overlap with menu choices (see the README), but you could do that, too, if you wanted to.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.