Not sure it is that much extra. They have the 5% overage too which is what this is close to.
They only had one senior in the top 10. Their 2nd and 3rd picks might end up a bit under slot. Miller should be slot or slightly above (remember being 19 I think he can go to college for 2 years and be back in the draft).
This is just the Phillies balancing most every penny they have in a somewhat conservative strategy to sign every pick they make with no room for real high dollar fliers like in the past. Hettiger is this year's Logan O'Hoppe pick just earlier. Not really enough pool room for a more expensive Emaarion Boyd type this year.