Yes I understand. This will depend on the aggregation strategy you choose for the category in which you put your grade item (if you haven't set up categories, it is the course category's aggregation strategy to which I'm referring).
These aggregation methods are described in this documentation. For some of them, the value you attach (in your mind) to different values isn't relevant, what matters is the minimum value, the maximum value and the grade value. For example, if you have 5 items in your scale:
4. Very good
Then giving a grade of 4 (very good) is equivalent to 80% of the maximum grade, and it is this ratio (0.8) which will be used in aggregating the total score.
The main restriction of scale values is that you cannot give arbitrary values to each scale value. You can't give 1 (appalling) a value of 0% while giving 2 (passable) a value of 40%.