The direness of a text message exists in an inverse relationship to its length. Compare:
"Call me whenever you get a chance."
"Call me when you can."
Or, even more chillingly:
"Call of." (that is, if you use T9 instead of the 'press 1 three times for C' text input method)
Considering the effort it takes to compose even a medium-length missive with your thumb, it's understandable why this inverse relationship exists. The spirit may be willing to 'scribe a lengthy monologue on the urgency of a telephone call, but the thumbs can only do so much, and at least in the States, text messages are generally limited to 160 characters (I vaguely recall a similar limit in Sweden, at least with Nokia).
Therefore, #1 gives the impression that the texter is calm and collected, and able to successfully thumb in 32 characters (including spaces) without mishap. Perhaps he or she is sipping tea and eating cucumber sandwiches in a downtown café, and desires the pleasure of your company, or at least your conversation.
#2 is somewhat less wordy, but still doesn't leave the reader with any particular sense of unease. The composer of the message has some important and potentially irritating news to impart, but it likely isn't too bad.
#3 sends chills up a person's spine --- how would you react if your mother or significant other texted you with this cryptic eight-character message? I imagine this must be the same feeling that Captain White must have felt when he came upon the eerie silence of the abandoned Roanoke Colony, and found the word 'Croatan' carved into a post. It's so short, that the imagination is left to manufacture its own worst fears.
But #4 is perhaps the most chilling of them all. The texter was compelled to compose a message as brief as #3, but was unable to check if the key sequence '63' resulted in 'me' (the intended word) or 'of'. The imagination gets the impression that the texter is compelled by a Lovecraftian compulsion to keep texting, even while being devoured, and is mere seconds away from impending catastrophe.