Trying to conceive

Hey ladies ! So my husband and I are trying for our first kid together. This is my first time using this app since in not really sure how to time things right. The app predicted that my period would end on a Sunday but mine ended on Friday night. Do I count 7 days from Friday to try for a kid? Or do I continue to count 14 days from Monday when my period had started?

We are really excited for our first baby and want to get this right. It has been 3 months so far since we have started trying. Any tips and tricks please feel free to let me know :) thank you.