Well, SASS, and SCSS are basically the same thing. (SCSS means “sassy CSS”). The difference is that with SASS, you remove a lot of the “boilerplace” characters, especially curly braces an semicolons.
So, this would be valid SCSS (and in this case valid CSS):
and this would be the same in SASS:
See, it’s the same thing, just with the “extra” stuff removed.
So, SASS and SCSS are basically the same thing. The difference between them is that they add extra features on top of CSS. Another observation is that CSS is valid SCSS but it isn’t valid SASS (unless you remove all the “extra” stuff.)
So, you can either call what you have SASS and get rid of the “extra” stuff. Or you can call it SCSS and change the preprocessor (by clicking on the settings icon next to “CSS” at the top of the CSS pane).