If you want to give your files a unique number based on the EXIF shutter count (sometimes also named
number of actuations or similar) you can do that by adding a step of type Text, and insert the metadata variable corresponding to the metadata tag holding that information.
For example, for many Nikon cameras, the metadata tag
Nikon::Main\167\ShutterCount\0 contains the shutter count. You can find this tag, or whatever tag your camera uses, easily in the Metadata Panel using the Browser layout (which shows all the data in your file).

Use the
Copy as Variable command to copy name of the corresponding variable into the Clipboard. Open the Renamer, add a new Text step and paste the variable into that step.
Potential PitfallDepending on the value of the shutter count variable, IMatch may format the result of the variable using thousand separators (this depends on the locale data and numeric settings in Windows). But adding a shutter count of '40.204' to a file name will cause an additional dot - and this is not a good idea. File names with multiple dots (aka extensions) may confuse other applications.
To strip the dot and to ensure that the number has a minimum width, independent from the actual value, you can use the neat
numformat variable formatting function. This function allows you to change the numeric formatting of variables, and their output width (how many digits).
Final ResultThe final Text step uses this variable:
{File.MD.Nikon::Main\167\ShutterCount\0|numformat:int,06}and looks like this:

You can look up all the details in the IMatch help file. Just search for
Renamer or
Metadata Panel or
Variables to find the corresponding help topics.
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