H4 visa appointment form - which Receipt Number to fill

I am on an H1 visa. I am applying for an H4 visa for my wife. We both have the I -797 extensions while in the USA. My wife is going for stamping in India. I finished DS160 and trying to get the visa appointment. I am filling out the form on http://www.ustraveldocs.com/. I am confused in the section PETITIONER and need some clarification. Please help me if you know the answer. As there are two receipt numbers including my I 797 and my wife’s I797.

Principle Applicant’s Name: [My name]
Principle Applicant’s Visa Class: [H1]
Petitioner’s Name: [My employer]
Start Date: [MM/DD/YYYY]
Receipt Number: my I797 receipt number or my wife’s 797 receipt number ???
Expiration Date: [MM/DD/YYYY]

Please let me know if I should use my I797 receipt number or my wife’s receipt number in the above form.

This will be the primary H1B holder’s information.