If guy has crooked smile across hallway?

I was walking down the hallway with my friend and say this guy infront of me 20ft away and he had this look on his face -->https://i.imgur.com/DXn70dc.jpg this is not the first time I saw this guy. Before he had serious look on his face almost like he was zoning out but this time he had grin on his face. whats the difference between these looks?
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If guy has crooked smile across hallway?
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