What does it mean when a guy who likes you is dry texting you (read for details)?

the thing is that one guy at school probably likes me (i'm 99% sure though) and few days ago we started chatting on instagram. he texted me first but it was pretty dry. then i had to keep the conversation going, but at least he hasn't left me on "seen". however, his answers were short and simple. also, he's a bit older than me and i'm experienced with people older than me being dry. in addition, he's very social and always talking to many people, so maybe just texting is boring for him.
before i end this i'll tell you reason why i'm sure he likes me. well, lately he's been talking to his classmate, with whom i started talking few months ago. that classmate was even talking to me in front of that guy and once he turned his head and kept watching us for a while (absolutely for no reason). and then i've been seeing them together a lot. also, few days ago i saw him talking to another guy, who is not in the same class as him, who i lately befriended as well. it's all about small details, so it's complicated to write everything here, but i hope it helped you to understand my situation better. thanks for answers + you can ask any questions.
What does it mean when a guy who likes you is dry texting you (read for details)?
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