This is defined in The US Office, Season 9 by Kelly Kapoor, on hearing Daryl's text's to Val where he wrote
"You're such a great friend....."
Kelly responds with:
"5 Dot's Daryl, are you kidding me. Okay, 3 Dot's means to be continued, 4 Dot's is a typo, but 5 Dot's means "Whoa, do not make me say what I want to say baby, but if I did, it would blow your mind Dot Dot Dot Dot Dot"
Five dots means someone has something to say, but they don't want to say it. Usually relating to having a crush or liking someone without wanting to tell them. Three dots (...) is just to fill silence when someone doesn't know how to continue a conversation. Four dots (....) are sent when someone asks a stupid question and will not be giving an answer.
"Three dots means 'to be continued,' four dots is a typo, but five dots means 'Woah. Do not make me say what I want to say, baby, but if I did, it would blow your mind.' Dot dot dot dot dot." -Kelly Kapoor