If a guy always kind of smile and ask "Why are you here" everytime I go and see him, is it good or bad?

We're not dating, more like colleagues. Everytime I just randomly go find him at work place when he's working and I'm not, he always kind of smile (not the big ones) and ask me why am I here. He never sounded shocked/irritated and I'm pleasantly surprised. I'm not sure if his behaviour is a good thing?

If a guy always kind of smile and ask "Why are you here" everytime I go and see him, is it good or bad?
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