I believe he meant to say 9 existing built in the CBD since 2008 and 2 U/C which the combined total is 6 million SF. In order of size and rounding size:
1. Block 58 (former Chron site) 1.1 million SF U/C
2. 609 Main 1.1 million SF
3. 811 Main (formally BG Group Place) 972,500 SF
4. Hess Tower 845,000 SF
5. Capitol Tower 778,300 SF U/C
6. Hilcorp Energy Tower 406,600 SF
7. GreenStreet (Retail & Office) 305,000 SF
8. NRG Tower (at GreenStreet) 263,200 SF
9. Partnership Tower 115,000 SF
10. 1712 Pease (small bldg 2009) 20,000 SF
11. 1201 Congress (small) 5,700 SF