If you provide a screenshot or any sort of visual presentation, it'll help us better understand the issue.
However, based on what you said, I suggest checking the ISFIRSTOCCURANCE() function. It'll allow you to only count a person once when (s)he appears for the first time and ignore all subsequent appearances.
Einas "Give a Man a Fish, and You Feed Him for a Day. Teach a Man To Fish, and You Feed Him for a Lifetime"