David B, it's possible with so few carbs and fat. There are 4 calories in a gram of carb or pro, and 9 in a g of fat.

300 x4 =1200 protein cals
50 x4 = 200 carb cals
25 x9 = 225 fat cals

If you add those 3 together that's 1625 calories. Make sense now?