I'm not sure where you get all this information from, but from what I've read, the PL recommended a punishment of 6 points, plus one additional point for each £5m expenditure above the threshold. To me that should be 6 points for a failing of £0-£5m, 7 points for £5m-£10m, 8 points for £10m-£15m, 9 points for £15m-£20m. Everton failed by £19.5m, so that's a 9 point points deduction recommended by the PL, from my understanding.
It could be argued that failing by £0-£5m should invite an additional point deduction, and each other band increasing by a point, resulting in a 10 point recommendation for Everton. I have read that the PL has guidelines for P&S failures, but these guidelines are not published in the PL Handbook, and I haven't found them published elsewhere.
The commission decided against using the PL recommendation, but applied is own sanction, which happens to be very similar to the recommended sanction.
This is in Section 13 of the Everton judgment document.