From NFL.com
Pittsburg 320 Passing Yards
San Diego 235 Passing Yards
Total Passing Yards 555 Yards
I believe you have the Tiebreaker result incorrect.
Maybe I'm reading it wrong but the last few weeks I've been using Total Passing Yds, not Total Net Passing Yards. The Tiebreaker says:
TIEBREAKER: TOTAL NUMBER OF PASSING YARDS COMBINED BY BOTH TEAMS.
From NFL.com...
<TABLE class=gc-team-leaders-table cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR class=thd2><TD>Passing</TD><TD>CP/AT</TD><TD>YDS</TD><TD>TD</TD><TD>INT</TD></TR><TR class=tbdy1><TD>
P. Rivers</TD><TD>21/36</TD><TD>
254</TD><TD>3</TD><TD>0</TD></TR></TBODY></TABLE>
<TABLE class=gc-team-leaders-table cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR class=thd2><TD>Passing</TD><TD>CP/AT</TD><TD>YDS</TD><TD>TD</TD><TD>INT</TD></TR><TR class=tbdy1><TD>
B. Roethlisberger</TD><TD>26/33</TD><TD>
333</TD><TD>2</TD><TD>0</TD></TR><TR class=tbdy1><TD>
M. Moore</TD><TD>1/1</TD><TD>
6</TD><TD>1</TD><TD>0</TD></TR><TR class=thd2><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR class=tbdy1><TD>
Total: 593</TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR class=tbdy1><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR class=tbdy1><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR class=tbdy1><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR><TR class=thd2><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD></TR></TBODY></TABLE>