When ratings are used in a forum or glossary, for example, and "Sum of ratings" is chosen as the aggregate type, that sum will never increase beyond the top of the scale for any individual rating. So if the rating is on a scale of 0-100, then as soon as the sum reaches 100 it stops there and never increases any further. This is not, therefore, a sum.

The help item next to the ratings setting reads "Sum - All ratings are added together. Note that the total cannot exceed the maximum grade for the activity.".

The problem is that the maximum grade for a forum or glossary activity is equal to the maximum value of any one rating (as defined by the "Scale" setting). This makes no sense, since they are separate things. It also leads to an absurd situation where a single student can give a rating of 100, and then everyone else's ratings are irrelevant, since the sum will never advance beyond 100.

There should be two independent settings: maximum grade of activity, and maximum individual rating. If the sum of ratings is to be used as a grade (which is not necessarily the case), it can be scaled to the maximum.

Steps to reproduce (in Glossary)
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1. Create glossary
2. Set Ratings > Aggregate type to "Sum of ratings"
3. Set scale to 10, and save
4. Add a new entry
5. Log in as a different user with permission to rate glossary entries (e.g. Teacher)
6. Give the entry a rating of 4 (A)
7. Log in as another user with permission to rate
8. Give the entry a rating of 5 (B)
9. Log in as a third user with permission to rate
10. Give the entry a rating of 6 (C)

Desired behaviour
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(A) Aggregate rating is displayed as "Sum of ratings 4 (1)"
(B) Aggregate rating is displayed as "Sum of ratings 9 (2)"
(C) Aggregate rating is displayed as "Sum of ratings 15 (3)"

Actual behaviour
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(A) Aggregate rating is displayed as "Sum of ratings 4 (1)"
(B) Aggregate rating is displayed as "Sum of ratings 9 (2)"
(C) Aggregate rating is displayed as "Sum of ratings 10 (3)"