Complex sentence: For this election, the NDP instituted a modified one member one vote system in which the vote is calculated so that ballots cast by labour delegates have 25% weight in the total result, while votes cast by party members have 75%.
Split into simpler sentences: For this election, the NDP instituted a modified one member one vote system. Votes by labour delegates accounted for 25% of the total result, while votes cast by party members accounted for 75%.