The Mask option lets you specify what you want your Unique Parameters to be specified as

Example, if you had a mask of 0000, your unique numbers would be something like

• 0001
• 0002
• 0003
• etc...

If you had a mask of xx, then your unique numbers would look like

• x1
• x2
• ...  (skipping 3 through 8 for simplicity)
• x9
• 10
• 11
• etc..

you could have a mask of just 0, in that case, it would look like

• 1
• 2
• ... (skipping 3 through 8 for simplicity)
• 9
• 10
• 11
• 12
• etc...

As with most things with File Renamer, feel free to play with different settings and click the Preview button to see how it would look.