How many people were sitting at the table in order of phoenix?

There were 13 people sitting at the table in the Order of the Phoenix headquarters during the Order's meeting in the fifth book.

Here they are:

1. Harry Potter

2. Ron Weasley

3. Hermione Granger

4. Sirius Black

5. Remus Lupin

6. Nymphadora Tonks

7. Alastor Moody (actually Barty Crouch Jr. disguised as Moody)

8. Kingsley Shacklebolt

9. Arthur Weasley

10. Molly Weasley

11. Fred Weasley

12. George Weasley

13. Ginny Weasley