15 seconds.

>>393208
It's been ten minutes. Is there also a numerical limit?

>>393212
I can't confirm this, but I've heard that there's a limit to the number of reports you can file in a 24-hour period. That's probably it.

>>393220
There is a limit, but it gives you a specific message that tells you when you've hit the limit.

>>393212
I've had this happen a few times when reporting multiple posts in a short amount of time. Could be congestion from the system trying to keep up processing them.