Display Number Variable in a notification

According to the documentation:
"Using Global Variables in Notifications

"You can put the value of a Global Variable in the message sent for a notification. Simply put the name of the Global Variable in curly braces, as in {My-Variable}, in the string for the message."

I have a global variable, vOpenDuration, that is a number. When I put it in curly braces for a message sent for notification, it displays as {vOpenDuration} and not the number.

Do I need to convert the variable from a number to a string to display it in a message or something else? How would I do that?

The correct format is %vOpenDuration%. The GV can be any type (string, number, or decimal) it may even work the boolean, but I haven't tried it.