Delegates system, world over, is used by political parties to nominate flag bearers, though it varies in terms of actual methods. The US, for instance, uses the caucus method, where party officials become the Electoral College or ordinary party members vote and the winner is known State-by-State.
Here, Deputy Prime Minister Musalia Mudavadi is championing ODM sub-branch officials to become the Electoral College at the counties. He wants each county to have 60 officials from sub-branches (constituencies). The county delegates will therefore be 60 times the number of sub-branches.