The constant for grain absorption is not in the mash or equipment profiles. It is a global setting and can be found by clicking 'options' >> 'advanced'. There are two figures: one for standard absorption and another for BIAB profiles. The BIAB grain absorption number is only used when the mash profile is set for 'BIAB with full boil'.
Note to Brad: It would be good to have this adjustment moved into the equipment profile for those of us who do BIAB with a batch sparge and also have a separate mash tun set-up for larger batches.