Case statements work from the top down and exit out as soon as they find a match, so if you put your statement in a logical order such as evaluating from smallest to largest, you can properly work through the different scenarios.

In your scenario, I'm guessing you want "Good" to be less than .06, "warning" to be less than .07 and then "bad to be anything else. You can set it up like this....

CASE WHEN ... <.06 THEN 'Good'

WHEN ... < .07 THEN 'Warning'

ELSE 'Bad'

END

Also, I would suggest either moving your error logic to the outside or replace 'Error' with 0. Otherwise it is going to try and divide 'Error' by Queued minus 'Error' which won't work.