From the Tournament Rules:
"If you receive one of the best 156 scores in the Qualifier round (or
one of those tied in the 156th position) to qualify for the
Championship, you may enter the Championship by logging in to the
website at www.wgt.com or www.USOpen.com,
between 1:00 am PT June 22, 2009 and 11:59 pm PT June 23, 2009 (the
“Championship Period”), and playing and completing the 18-hole stroke
play game between 1:00 am PT June 22, 2009 and 11:59 pm PT June 23,
2009."