Not intuitive (Apple Watch

Thought this would be great since its meant to work with the watch, but when I try to add that I drank a glass of water (Ive set 8oz glasses of 8 glass daily goal) it says "1.5 of 8 glass". Why is it working in decimals? Will look for another app.

westsidegirll about Daily Water - Drink Reminder, v3.6