4# at .6 ppm will yield 1.1 mg Se.
(4 divided by 2.2= 1.8 Kg 1.8 X .6 ppm= 1.09 mg Se)
Are you reading the mineral blend correctly at 20 mg/#? (not 20 ppm?)
Is there a reason why you need to feed the entire 2 oz recommended portion? That amount probably doesn't take into consideration that you are also providing some type of fortified concentrate that is going to provide a certain amount of vitamins and minerals.
The short answer is yes, the recommended amount of Se is 1-3 mg but it's a little more complex than that as it's a % (ppm really) of the entire diet included the hay. You are well within the safe zone even at 4 mg.