If he smiles at me and I don’t smile back will be assume I’m not interested?

I was at the gym and I looked up from what I was doing to see him looking at me and he smirked at me, and I just made eye contact and then looked away.
he then after it seen me struggling with my weights whilst I did chest press
and I could see him quickly notice and come over and help but I managed to get it up off me myself before he got over to me. Will he probably think I’m a bitch or I don’t like him because I didn’t smile back
If he smiles at me and I don’t smile back will be assume I’m not interested?
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