If you just want to give unnumbered files a number, the On gap-gadget will not be of further interest. It's only of interest, if you Renumber files, and some of the numbers are left out (gaps).

• Pic.xxx (xxx = 000-009)
• Pic.yyy (yyy = 020-024)
• Pic.zzz (zzz = 030-039)

You can see that files with the numbers 010-019 and 025-029 aren't existing, these are gaps.

When ProRen starts to rename the files, it depends on the OnGap-Gadget, how ProRen reacts when it comes to rename the files Pic.020 and Pic.030.

In the examples for Leave and Close the Index is 100.

Leave means that 000-009 will be renamed to 100-109,

• 020-024 to 120-124 and
• 030-039 to 130-139.

The gaps and their sizes are kept.

Close kills the gaps. This means that the files

• 000-009 will be renamed to 100-109,
• 020-024 to 110-114 and
• 030-039 to 115-124.

After the gaps have been killed, you have one single Chunk of numbered files.

If the GapMode-Gadget shows Ask, you will be asked via requester for every gap, if it should be kept or deleted. You also may abort the renaming procedure at such requester. This can be undone, though some files already have been renamed.