To be able to pass in a Sass command line option and have it include the true line-number of the css selector, into the style properties of the generated css file. This will allow you to easily jump to the line number for a selector vs having to try and do a [ctrl/cmd + f] in your code. This is different than [:debug_info] as it will actually include the line number in the css code that the browser shows us. For example:
sass --watch --style :expanded :line-numbers sass:css