Job Recruitment Website - Immigration policy - Why is the US visa receipt posted on DS 156?

Why is the US visa receipt posted on DS 156?

1. The first copy (yellow) is taped to the last page of the form (one * * * three pages). When pasting the invoice, please be careful not to block the barcode area.

2. The second copy paper (blue) should also be brought into the embassy. Take it, and the embassy staff will put it in their hands and return it to you. (Reimbursement receipt)

3. The first copy (yellow) was collected together with the 156 form.