If this box is un-checked then flange design bolt load for the gasket seating condition is computed as:
W = Sa * ( Am + Ab ) / 2
Otherwise it is computed as follows according to note 2 of App. 2-5 of the ASME code:
W = Sa * Ab
This equation can be used when additional safety against abuse is desired.
Where,
Sa = bolt ambient allowable stress
Am = total required bolt area
Ab = total available bolt area