good question, I’ve tried this so many ways, you can empty the mash then add the water then stir then empty again or trickle water over the top then empty just as slow never stirring but as far a water amounts I laugh at people trying to hit the exact amount with sparging, you’re going to use water cleaning any way but the answer is doesn't matter how much water is in the hlt you stop when the kettle is at its mark then use the rest for cleanup, I always have extra because you don’t want the last bit of husk and solids in your boil kettle, it just converts to trub anyway