If information disclosed in accordance with this part is subsequently rendered or discovered to be inaccurate as a result of any act, occurrence, information received, circumstance or agreement subsequent to the delivery of the required disclosures, the inaccuracy resulting therefrom does not constitute a violation of this part; provided, however, that at or before closing, the owner shall be required to disclose any material change in the physical condition of the property or certify to the purchaser at closing that the condition of the property is substantially the same as it was when the disclosure form was provided. If, at the time the disclosures are required to be made, an item of information required to be disclosed is unknown or not available to the owner, the owner may state that the information is unknown or may use an approximation of the information; provided, that the approximation is clearly identified as such, is reasonable, is based on the actual knowledge of the owner and is not used for the purpose of circumventing or evading this part.