I am filling out W7 form for my wife, she came here on F2 but how her status is H4. Her passport still has F2 visa stamp since we have not been out of the country since.

What should I put in question 6 c) Type of U.S. visa (if any), number, and expiration date,

Thanks for your help.

Put "H4" and the document number from the approval certificate, plus the expiration date.