They ignore 54 delegates in PA (it has 71, not 17) because by some arcane rule they are somehow uncommitted. I have to believe most of them go to Trump.
I think he also shortchanges Trump in NY, and likely CA.
And those are just the three states I looked at. Silver works for the NY Times. They have an agenda.
Interesting commentary on the individual states rules here:
http://blog.constitutioncenter.org/2016/03/the-gop-nomination-math-confusing-and-complicated/
Also Nate has Trump at 695 delegate
RCP has him at 739 and I have seen others a little more/less
But 695 is the lowest number I have seen
This guy is a fraud