App question

I have a question regarding when you finish eating for the day and you click on finished logging in for the day. If I don't eat all my calorie intake I had 355 cals left on Sunday that it said I would lose 8lbs in 5 weeks. I ate a bit more yesterday but still had calories left and it said I would lose 5lb in 5 weeks, today I ate most of my calories with 2 cals left and it said I would lose 3lbs in 5 weeks. I am thinking to myself I want to lose 5lbs in 5 weeks so should I be eating less than it's telling me to? How do I change my target?