Placeholder for unknown number of digits

1. What is a placeholder for an unknown number?
2. How do you add a variable to a placeholder?

What is a placeholder for an unknown number?

Variables are placeholders for unknown numbers in expressions.

How do you add a variable to a placeholder?

To add a placeholder field for a variable

In the Placeholder type box, select the variable type you want the placeholder to reference. In the Field properties box, under Variable, type the name for your new variable (or select an existing variable from the drop-down list). For a new variable, click Create Now.