Unfortunately it does not look like there is a way for an admin to manually change the total score of an Idea in Jive. This may be something you post over in Ideas for Jive as something to request for a future version of Jive - I am sure there are others in the community who would also see the benefit of this. Our product managers review that area for feedback when considering what new features to include in the platform.
Thank you, David.
I'll submit an idea.