Without trying to sound flippant, it means exactly what it says. If you own 100% of the property, then it would be 100% of the current fair market value. If you own 30% of the property, then the debtor's interest would be 30% of the FMV. Joint tenancy would be something else again.
How you present numbers on your petition and schedules can have a huge outcome on how your case proceeds including what you can protect. You need to be sure you are accurate but presenting the information in the most favorable light to you.
You may wish to review some reasons why hiring a bankruptcy attorney is important.
If you represent yourself, you are responsible for knowing all the laws and procedures pertaining to bankruptcy.
Mark Markus has been practicing exclusively bankruptcy law in California since 1991. He is a Certified Specialist in Bankruptcy Law by the State Bar of California Board of Legal Specialization, AV-Rated by martindale.com, and A+ rated by the Better Business Bureau.