Adjustment of Status - I-485

HI EVERYONE, I APPLY FOR I130 AND I485 ON AUGUST 2014, I GOT ALL THE RECEIPTS WENT FOR BIOMETRICS AND 2 MONTHS LATER I GOT THE LETTER SAYING NOT ENOUGH INCOME, SO I COULDNT FIND AN AFFIDAVIT OF SUPPORT BEFORE THE DEADLINE, THEY DENIED MY I485 SO I THOUGHT THERE WAS NOTHING TO DO ABOUT IT, BUT ON AUGUST THIS YEAR I RECEIVED A LETTER FOR AN INTERVIEW WE WENT TO THE INTERVIEW IT WENT WELL WE GOT THE I130 APPROVED THE SAME DAY THAT WAS SEPTEMBER 11, 2015. NOW I GOT THE AFFIDAVIT I RE APPLY FOR THE I485 AND THE CASE STATUS IS SAYING THIS "Case Is Ready To Be Scheduled For An InterviewAs of November 27, 2015, we are ready to schedule your Form I-485, Application to Register Permanent Residence or to Adjust Status" , MY QUESTION IS DID SOMEONE WENT THRU SOMETHING LIKE THIS? WHY THEY WANT ANOTHER INTERVIEW ? IF WE ALREADY GOT THE I130 APPROVED?