Guy's Behavior

What does it mean if a guy smiles and head nods at you and raises his eyebrows up and down?

my crush saw me from afar and as soon as he saw me stared right at me. I could tell he tried to act cool and just walk to his class by me and looked right at me and smiled, head nodded, & I noticed he raised his eyebrows up and down twice. any thoughts or what does this mean?
What does it mean if a guy smiles and head nods at you and raises his eyebrows up and down?
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