Staff Search - Job Star Rating - what does it actually represent?

I was re-setting up my columns after a format and I noticed a column type in the Staff Search screen called "Rating (General)" - there are two of them, one relating to job and the other to preferred job. Now I understand the difference between those two, but the actual stars don't make sense. For example, on this screen, it says that my goalkeeping coach is 4 stars (both "Job" and "Preferred Job" - because he's in his preferred job) however the star rating under the Training/Coaches screen is 4.5 stars.

So what does this rating actually mean/apply to? And who's opinion - if any - does it reflect?