Her hand on my shoulder?

I was invited to a Saturday game night event at my friends house, there were a lot of people there, we gathered around to play a board game.

As we were about 21 people, I was talking to the people that were next to me, till I realized that a girl was asking my friend who am I and she was explaining to her that we work together etc, I noticed that she was looking at me from time to time, could be innocent looks.

When she was leaving, I was the only guy which she laid her hand on the shoulder and said ‘good bye’, I didn’t even talk to her the whole evening, but her laying her hand on my shoulder got my attention, what do you guys feel about this?

When you put a hand (especially girls) on a guys shoulder what does it mean?
Her hand on my shoulder?
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