The example shows a "state" with 50 voters where 60% of voters are "blue" and 40% are "red" but through selection of district boundaries one can get results of 5 blue districts and 0 red districts to 2 Blue districts and 3 red districts even though using a "standard" redistricting one would expect 3 blue and 2 red.
This case is from Wisconsin where:
The plans, developed in 2011 by Republican leaders who controlled the legislature and signed by Gov. Scott Walker (R), were effective.
In the election held after the new district maps were adopted,Republican candidates won 48.6 percent of the statewide vote but captured a 60-to-39 seat advantage in the State Assembly.
Evidence uncovered during lawsuits over the redistricting found that models showed Democrats would have to win about 53 percent of the statewide vote to capture a bare majority of the seats.The swing vote (as usual) is Justice Anthony Kennedy.
Hat/tip to Wonk Blog