i'm guessing here, but i could do the math if i had all the dimensions...
the valve starts to open early at 11 before TDC, but it's not like an on/off switch, likely the valve still has plenty of clearance by the time the piston passes TDC as the camshaft has only rotated 5.5 degrees into it's opening for the 11 degrees of travel the crank had to do.
-s
