This combines all your css into one file with then creates a different name each time. This means browsers will always load your css if there are any changes:
that changes to the css file are not showing in your browser?
or that changes to your sass files are not compiling into a css file?
If you are talking about number 1 then - as a test - have you tried changing the name of your css file? This will guarantee that your browser reloads the css file