Complex sentence: The 6th Congress was attended by 3,062 delegates with voting rights and 158 without them; this marked an increase of 1,349 voting and 137 non-voting delegates from the 5th Congress.
Split into simpler sentences: The 6th Congress was attended by 3,062 delegates with voting rights, and another 158 delegates with no voting right. There was an increase of 1,349 voting-right and 137 non-voting right delegates from the 5th Congress.