For the interview I was maybe asked around 5 questions very bluntly and then told that my joint sponsor did not make enough money to meet the financial requirement. I was caught off guard by this as I know my sponsor makes more than enough so was not prepared to argue my case on this issue, and did not memorise the ins and outs of US tax laws and paperwork. After I left and looked over my sponsors tax documents again, I realized that the officer most likely only read the amount stated on the W2 and not the Form 1040 that we had also submitted. If he had checked this he would have realized that we easily met the financial requirement, but the 1040 was never mentioned.
Also, the documents had already been accepted on CEAC so I'm not sure why they waited until the interview to tell me that his income would be a problem. If they'd told me at any point before the interview then I could have come prepared with an explanation. In any case I am not sure why they would ask for a Form 1040 if they do not read it. So as a result of this I was given my passport and other original documents back and a green 221(g) asking for his tax transcript or another W2. The instructions are vague and I don't really know where to go from here.