[NTG-context] Row span in tabulate

Hi, I am making a table using \starttabulate … I want row expansion last 3 columns and put a title “q” at the center of last 3 clolumns. I \NS[3][c] following the example in the wiki. However, it doesn’t work. The following code run without error message, but “[3][c]” appeared at the beginning of the first row in the output. How can I do that? Thank you. Best regards, Dalyoung