everything from your IMEI to phone number to IP and all possible uniquely identifiable elements are sent to IG at the time of registration from your device. If

everything from your IMEI to phone number to IP and all possible uniquely identifiable elements are sent to IG at the time of registration from your device. If you have like Xprivacy you can see the app go through requests for a variety of data + constantly phones home (like all apps). FB wants to make sure your new profie is engaged and active, so they'll use this data to nudge you into standard on-boarding processes.