What does it mean when a guy pats a girl on the head?

I'm 5'6" so I don't consider myself that short, which is usually why I pat other friend's heads. But my guy friend likes to pat me on the head...

It makes me wonder how he sees me though -- "silly/cute little sister" or "cute girl I wanna date."
What does it mean when a guy pats a girl on the head?
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