Counting the delegates for a candidate should be the most basic exercise and an easy task. This however is not actually the case, as you will see in the video below.
The numbers that we use are “best estimate.” This is due to the votes cast locally and what the rules state, that is why we use “estimate.” They are arrived at by use of several news agencies. As an example in states that have yet to vote; there are delegates that have been awarded. Those numbers are counts that have been concluded by the Associated Press (AP) or other agency. In the case of the AP they have been historically accurate counting of non-pledge-able delegates or automatic delegates such as a Chairman or Committee man/woman.
The numbers that are used such as in Iowa, or other caucus state, are accepted numbers used by the bean-counters in the media and those they are political junkies. Those delegate counts are fluid until there is an actual elected delegate: yes, we do expect that they will change.
Using Iowa, the count is based on how the local caucus voted. However what did happen was that local delegates were elected, they may in fact not be supporters the local caucus winner. Those delegates will move up the ladder toward a point when there will be an election of an actual convention delegate.
That is the point when the delegate count will turn and it is possible to arrive at closer to true count of the delegates. Please refer 2012 Republican Delegate Count.