It is interesting to watch this, and we are all learning a lot about the process.

The DNC rewards different things, such as having voters from a wider area, thus suppressing the votes in populated areas.  This has actually worked against Obama, although in NV it worked against Hillary.

Another rule is that the candidates have to have staying power.  Apparently, more of Obama's delegates than Hillary's showed up in the next tier of the election, so she lost a delegate.  The selection process begins with a popular vote, but it isn't a 1-1 representation.

The electoral math can be just as elusive.  It's possible to win the election without having the popular vote.

Personally, I'd like to do away with all this funny math and get back to real representation in both the primary and general election.  But, this is the system we have.