I heard it was 30. Regardless if its' 25 or 30, the rest of it gets turned to fat or used up if you workout. Anytime anyone eats a lot of protein, the kidneys work extra hard. Give em a break by drinking a lot of water with whatever protein source you are intaking to flush out the system of wastes.
Also, to the girl that eats the tuna at work: See if you can bring a small tupperwear container. When you open the tuna, Eat only half of it and take the half of it and put it in the tupperwear and stick it in the refrigerator at work for later. If they don't have a fridge, bring a cooler with ice in it, and stick it in there. This will lessen the strain on your kidneys and you'll have food later to eat
Bring an apple with you to work and eat the tuna with the apple. Mmmmm