Complex sentence: In the eastern half it increased from about 90 million cubic meters per year to more than 140 in 2004 in line with contractual targets, but then declined to about 120 in 2007, far below the contractual target.
Split into simpler sentences: In the eastern half it increased from about 90 million cubic meters per year to more than 140 in 2004. However, it then declined to about 120 in 2007, far below the contractual target.