Seems like you have duplicate rows of data
One way to fix this is to use DISTINCT (sum(DISTINCT STK_OPEN)), but that won't work if each row have different values. Ideally you should fix this in the script itself.
Paul please don't open new posts for the same issue.
I allready pointed out the fact that there are 31 value entries for dec in this post.
And it has been confirmed here again.
You should check your datamodel for duplicates or check the JOINs you use.