But if I have to keep track of the fact that the partial favorable was a partial myself, doesn't that mean that management is only giving me 4 hours' credit for it?
You need to track cases yourself, in addition to the report you can run on CPMS MI.
1. because sometimes CPMS fails to give you credit for writing the case.
2. because unless you know what you've done, you have no basis to argue with whatever number management provides.
3. you need to push management to tell you what numbers they are using in evaluating you. They will likely refuse to share numbers re: other employees but should at least provide your numbers.
If you don't act to protect yourself, it's doubtful anyone else will.