Auto increase after 6 statements. If no auto increase is given, you can call and request a higher limit then.
I got two +$500 auto increases roughly at my 3rd and 5th statements. I have tried to request CLI online yesterday (after the 6th statement), but was given a message that they need to verify my info and that it will be a hard pull, so I haven't confirmed the request.
So they do give auto CLIs even before 6th statements, but at the same time 6th statement does not guarantee getting an automated CLI