I'm new

Hi. I am new to myfitnesspal. I am having trouble deciding which lifestyle to choose for my goals page. I am a full-time student during the week but when I'm not at class I'm at work which is mostly on the weekends. I work as a customer service clerk/cashier at a local grocery store. I usually rack up approx. 15-20 hours a week. Should I choose sedentary since I am in class and all I do there is sit for half a day or should I choose light active to account for my time at work?