This is a page from the Flash Renamer user manual.

Add Counter

This function will add a number sequence to your filenames. The first file will get the initial number and then this number is increased for each file. You can drag files up and down in the listview to change the file order and thus the enumeration index for the file.

Customizing the Counter

The counter is a global object that can be used in many situations, including the above "Add Counter" function. You can customize the counter to suit your taste. Read more about the counter object here.

Tip: Learn how to use the <counter> tag for full control of where the counter is placed in the filenames. Read more about format tags here.