When we mailed the AOS on July 15. My Mom filled Form I-864 with letter of explanation of not filing based on zero income and a publication from IRS. So, that was right since we did not get a checklist for hers. As soon as I read the I-864a checklist , I knew right away that I did something wrong on my form. On the initial AOS, I submitted the wrong form. I used I-864 for myself . But NVC wants me to use I-864a because on my Mom's I-864 on Part 6, 6a &7b she used our income (me &husband) so on #10 of Part 6 her current annual household income is not zero.
Anyways, we mailed the right and corrected AOS and IV packet at the same time on Aug 8 and NVC got it on Aug 12. My brother called NVC right after they got it and they said that they just entered the IV documents on Aug 15 with the corrected AOS. So another 20 business days to wait till completion hoping there's no other checklist.