The app made to help home brewers brew their coffee by calculating a the grams of water needed, and run a timer all in the same screen.
With Grams mode, the number you enter into the big box is coffee in grams and the large output is the water in grams.
When you are in TBSP mode, the number you enter into the big box is coffee in tablespoons and the large output is water in cups.
The bottom right box (18.5 is the default Grams value) is amount of water for coffee:water ratio So when you are in Grams mode, you get a 1:18.5 ratio and the water amount is changeable. I personally use 1:16.8
When you are in TBSP mode, You get a 1:0.375 ratio which is 1 TBSP to 0.375 cups of water ratio. This is also changeable.