Recall, state is unset|success|failed (etc.) with a reason (unset|build failed, etc.)
If a project's "state" is set to something bad (e.g. failed) then that propogates "up" to all "dependees" of that project that do not already have a bad state. When state propogates it changes (from whatever negative) to "prerequisite failed", and the originating project becomes the RootCause for these projects.
If a module's state is set to something bad (failed) then that propogates down to all it's projects, and in turn 'up' (to dependees of those projects). A module can be a RootCause.
A module's "affected" count is a count of all dependees where the RootCause is this module, or any of it's projects.
A project's "affected" count is a count of all dependees where the RootCause is this project.
Note: This means these counts are often less than the "total dependee count".