Q: Asked to change passcode from 6 to 4 digits within 23 minutes

A screen popped up on my iPhone asking em to reset my passcode within 23 minutes. I had to enter my old 6 digit passcode and then a new 4 digit passcode two times. Now when my phone is locked i only need to enter the four digit code (and it does work). Is this actually something apple has set up? I'm worried it's somehow from something else as a hack. Has anyone else had any experience of this?