Batch Size

Hi all

Fairly new to BeerSmith, finding it very helpful but struggling with my batch sizes.  I'm brewing on a small scale - aiming for just 8.0 litre batches but am only getting around 6.5.  My last recipe was all-grain BIAB using 11.8 litres of water, 2.56kg grain and boiled for 60 minutes.  Efficiency I estimated at 65% but this is a new set up so could be off by a few %.  Nothing special in my equipment profile:
Evaporation Rate: 18.5 %
Losses to Trub/Chiller: 0.00 l
Mash Tun Deadspace: 0.00 l
Cooling Loss (%): 4.00

If anyone can point out where I'm losing that 1.5 litres I'd be grateful.

It looks like you need to tighten up your profile.  On your next brew, measure your water volume going in (as you have done) but also after you remove the grain bag (pre-boil volume) and post boil.  Either you are losing more water to grain absorption than you have configured in BeerSmith or your boil-off is greater than 18.5% (or both).  You could also cut back on your boil rate some, as typically most aim for around a 10% to 15% boil off rate to control the amount of color and melanoidin development.