As I read it - distributions on such charts should be a single round or elongated blob in case of fair elections as there are natural statistical fluctuations between how people vote and how many of them vote in each individual voting precinct.

In top left corner you can see distributions of past elections from other countries - e.g. Czech Rep, Poland, Spain are examples of "good" distributions. On the other hand Russia '11, Russia '12, Uganda - are examples of rigged elections, where you can see main normal blob and kind of tail and another pronounced blob in top right corner (which means several voting precincts use fake ballots to acheive almost 100% voter turnout and virtually all votes cast for winner)

On the right is main chart which clearly shows abnormality because it is 3 very narrow groups rather than single big roughly round-shaped blob. This actually means centralized state-level cheating.

As I read it - distributions on such charts should be a single round or elongated blob in case of fair elections as there are natural statistical fluctuations between how people vote and how many of them vote in each individual voting precinct.

In top left corner you can see distributions of past elections from other countries - e.g. Czech Rep, Poland, Spain are examples of "good" distributions. On the other hand Russia '11, Russia '12, Uganda - are examples of rigged elections, where you can see main normal blob and kind of tail and another pronounced blob in top right corner (which means several voting precincts use fake ballots to acheive almost 100% voter turnout)

On the right is main chart which clearly shows abnormality because it is 3 very narrow groups rather than single big roughly round-shaped blob. This actually means centralized state-level cheating.