When designing recipes and setting the batch size it should be set for the post boil volume correct? That is technically the final batch size even though it won't all make it to the fermenter.
I set mine to the amount going into fermenter. I also have my hardware setup configured for what I lose to equipment, like the plate chiller, pump, bottom of the kettle, etc. Helps me to hit my target volume pretty much every time.
Batch size is typically the volume going into the fermenter. For us doing partial boil stove top brews we can only boil 3-4 gallons so we top off with water to 5 gal before adding to fermenter and the recipe batch size is then 5 gal. The OG and FG estimates are based on 5 gal volume.