It was the first time that I played with the Artistic Style tool today. So I first read the Artistic Style Formatter dialog help page and also the homepage of Artistic Style.

After first run I have seen that I can see the command line used by UltraEdit when calling Artistic Style in the prompt area (left side) in the status bar at bottom of the UltraEdit window. So I looked on the homepage of Artistic Style what all of them means and the last one -s# was the most interesting one because it specifies the indent spaces. But where does this value come from because it cannot be specified in the dialog?

The help page of UltraEdit for the dialog does not explain it - I will report that omission to IDM support (help was updated).

But I quickly thought in the right direction. The indent spaces value used is the value of Indent Spaces specified in the configuration dialog at Editor - Word Wrap / Tab Settings for the current file extension which was c on my tests with UE v13.00a.

See for example the forum topic extension based tab settings problem how to specify the tab stop value(s) and the number of indent spaces individually for files based on their extensions.