What does it mean if a guy didn't read my message but his 'last seen' was after the time I sent it?

Does anyone else's crush do this? He won't respond to my message for an hour or two at a time, but will be on snapchat a few times in between then. And he doesn't read my message until he actually responds.

To all those who are going to tell me to see him in person: I CAN'T RIGHT NOW!!

What does it mean if a guy didn't read my message but his 'last seen' was after the time I sent it?
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