I Exercise 5 Days A Week And I Struggled With

I exercise 5 days a week and I struggled with my weight in the past. I have recently noticed that my body is starting to look lean and strong and I eat in a really balaned manner in every meal. However, today I went to the cinema with my brother and we shared a box of popcorn and I was wondering how much that affects my gym gains of the week. Thank you for answering my question