You can ask that the seller fill out the areas in question and hope they return it or simply sign and have a contingency set up for your inspections. Your agent should know what to do here and should be going to bat for you in the respect.
You can return it and request it to be completed. Signing it usually acknowledging receipt of a complete disclosure, but if it's not complete you may not want to sign it.
One other thought, Seller's disclosures are helpful, but not reliable. A professional inspection from a very good inspector should always be done.