This generally applies to superscripts (index.html and Index-2.html).
This is a common problem, but this cannot be avoided!
For example, http://www.foobar.com/ and http://www.foobar.com/index.html can be identical pages. But if the links on the site link to both http://www.foobar.com/ and http://www.foobar.com/index.html , these two pages will be caught. And also because http://www.foobar.com/ must have a name, since you may want to browse the website locally (the directory / will provide a list of directories, NOT the index itself!), HTTrack should find it. Therefore, two index.html will be created, one with -2 to indicate that the file should have been renamed.
You might think that http://www.foobar.com/ and http://www.foobar.com/index.html are the same links to avoid duplicate files, right? NO, because the superscript (/) can refer to ANY filename, and if index.html is usually the default name, index.htm can be selected, or index.php3, mydog.jpg, or anything you can imagine . (some webmasters are really crazy)
Note. In some rare cases, duplicate data files can be found when a website is redirected to another file. This problem should be rare and may avoid the use of filters.