So what I'm reading from that is that you use BIAB and someone has given you a recipe kit usually sold for the grainfather.
If so, just use the same procedure you normally use.
I assume for your recipes you do some sort of calculation to work out the water, just use the same amount of water you would normally use for the amount of grain that is in your kit
Grainfather water calculations take into account the deadspace in the machine, and then they are just water per kilo of grain + sparge water to reach desired boil volume.
I don't know BIAB calculations at all but potentially, and this is very much a guess only, you could just take the water volumes, if any, mentioned in the kit instructions you received, if any, and take off 3.5L
Be far better off to calculate them yourself though...