I'd say about 3.5 gallons into the mash.
then 3.25 gallons of sparge water.
given the boil-off evaporation and the trub loss, this amount works well to get 5.5 gal in the fermenter, and then there is another 1/2 gal loss of the bottom ickies, which creates the perfect amount to fill a keg.
I measure all this in US gallons.
I didn't bother to measure the gravities.