Does anyone know when Twitter starts putting "Warning" to an external link in a tweet?

I use a bit.ly link and have noticed this error "The site you were trying to visit may be unsafe!" I did tweet the same link 12 times today in under 20 hours. Does Twitter do this when you tweet the same URL 5 times in 24 hours? or 10 times in 24 hours? I used a different bit.ly yesterday and got the same error but today I clicked on yesterdays links and no warnings. Thanks.

Nobody has used the same link on Twitter to test it out?

i am also getting the site you were trying to visit may be unsafe on my website link.