Complex sentence: At the 50th annual meeting of the EBU reference group in September 2007, it was decided that, with still more nations entering, starting from the 2008 contest onwards "two" semi-finals would be held, from each of which one could qualify for the final.
Split into simpler sentences: At the 50th annual meeting of the EBU reference group in September 2007, it was decided that from the 2008 contest onwards "two" semi-finals would be held. In 2008, with still more nations entering, there were two separate semi-finals, from each of which one could qualify for the final.