Recently, I have requested a couple of colleges where I’m going to apply this year to add me to their mailing lists. They both had a question regarding my school. However, because I have already graduated, I wrote “-” in that question instead of the name of my school. Only later did I realize that I should have indicated my past school if I have already graduated…
The colleges are very selective, and I worry that it may show me as a bit of a strange, not following the directions, applicant if I write “-” in the place of my school name.
Should I write an email to the colleges to apologize for the mistake?
Should I contact universities if I'd made a mistake while requesting to add me to the mailing lists?
No, they won’t care. It’s just a mailing list. They won’t connect your request to any future application.
Agree; you’ll get your chance to correct it on the application.
Thanks!
By the way, a follow-up question: do you know what happens if you send a request to join the college’s mailing list more than once? That happened by mistake in my case, and even though I made the requests quite some time ago, I didn’t get any mail from the colleges.
Sorry for many questions on a simple topic, but I am just a little confused by this process: sometimes I get snail mail and sometimes I don’t, sometimes get email confirmations that I was subscribed to the college’s mailing and sometimes I don’t. That’s why I ask if this all is normal 
Well, I’m pretty sure I’ve done it more than once on a few! I just assume that whatever happens behind the scenes in computer land just discards the second request. And your experience is what I have…sometimes confirmations, sometimes not, sometimes snail mail, sometimes email.