Are you suppose to eat up all your calories for the day?

Depending on how many calories you need a day, the number of calories you eat will determine if you lose or gain weight.

If you eat below your needed calories, you lose weight. If you eat the same, you will retain your weight. If you eat more, you will gain weight.

This is also on average over a course of time, it doesn't apply to every single day.

I think it really depends what calorie goal is set and if exercise was involved too. But generally you can still loose weight without eating at that goal. Might also want to look into macros count as well. I find that helpful.

look at an article or video on how the body loses weight. you need some info on how the body works.

it you just want an answer and don't want to understand how you lose weight then yes you will lose weight