URL Alias adding number to the end

YEEditor (alias: yeeditor)
- Installation (alias: installation)
- Technical (alias: technical)

YESlider (alias: yeslider)
- Installation (alias: installation-1)
- Technical (alias: technical-1)

YETemplate (alias: yetemplate)
- Installation (alias: installation-2)
- Technical (alias: technical-2)

When it is in the subcategories, with the same name it automatically add a number to the end.
How do we change this so it won't add the number to the alias?

I had checked your forum, and it doesn't do this, How do we achieve this?

Vincent