Thanks swimIan -- still a little confused. With BIAB profile, BeerSmith calculates 7.87 gal needed for 10.75 lbs, which puts me at in your range at 1.36. It gives me a strike temp of 157. It's saying that if I combine 10.75 lbs with all 7.87 gal at 157 deg, I'll achieve my mash temp of 152. However, as I will not have the full water volume in the mash tun to start, adding grain will likely drop me below 152.
But maybe I'm overthinking this... at initial dough-in the temp will drop below 152, but as the system recirculates more 157 deg water into the mash tun and reaches equilibrium, I would probably get back up to 152. Hmmm ......