I know there are individuals who did gain 20 lb on something like that, there are also individuals who gained 20 lb on the Parillo Diet or Cybergenics… Sometimes people make good gains even with what is a weak program, especially if fat and water gains are counted along with muscle, which is a very easy mistake to make.
As a rule of thumb, 500 mg/week total steroid is the minimal amount IMO for a mild cycle -- let alone one intended to give you as much muscle as possible as you say you want -- and your weeks 1-4 are 425 mg/week. Pretty much right at the minimal amount.
If you're set to make good gains anyway, your body is ready, you have the right training program and now you're hyped for it, you improve your nutrition... you may IMO gain 10 lb more than you otherwise would have if you are a high responder. Which could be 20 lb total.