Calorie deficit means consuming fewer calories than you burn each day. When you set up a health profile and target weight, Oatsy calculates the amount of calories you need each day.
Stay in Calorie Deficit by logging foods each day and keeping up with the goal. Check the progress screen often to see if you are "On Track" or "Over Limit" for each day.
Want to learn more about Calorie Deficit? Check out this page
https://www.oatsyapp.com/post/what-is-calorie-deficit-and-how-can-an-app-help