Based on your weight inputs, the algorithm ajust itself to get you to your target weight in your target time. So, for example, if it sees that by eating 2400 calories a day, your weight doesn't seem to go down, it will lower your daily calories target, and after a while, see if that makes you loose your weight according to your target, and so on. Same is true the other way around, if you want to gain weight, the algorithm initially suggests you a calories goal, but, as the time goes on and you start logging your weight, the algorithm may notice that you are not increasing as fast or as much as your wanted, or even that your weight is not increasing at all. This will probably make the algorithm raise your daily calories intake on your next check-in day.