Question on I-539 -Receipt notice

[degu]

Hi,

I had filed Extension of Visa for my In-Laws.(both of them) . I received only one Receipt notice on Saturday - where the name on the envolepe was the main petition holder, however when i opened the cover, i saw both the names - mail petitioner and supplement was listed on on the letter. Now my question is will my mother-in-law receive a seperate receipt or will it only be this receipt with only one receipt number? If any went receive anyting like this kindly let me know.
Thanks.

[immihelp]

One receipt for one application. If you filed together, you just get one.