The answer is based on the limited information provided in the question background. The 3600 funds are US Air Force RDT&E funds. RDT&E funds have a Current period of 2 years, during the current period funds are available for obligation, expenditures, and adjustments. After the current period, the RDT&E funds move into the Expired period which lasts for 5 years. During the expired period funds are available for expenditures and adjustments, no new obligations. After the Expired period the funds move into the Canceled period, at this time the funds are no longer available and are pulled back up to Treasury. An example of the fund life cycle: FY 2018 RDT&E funds - current period FY 2018 and FY 2019; expired period FY 2020, 2021, 2022, 2023, and 2024; canceled period begins in FY 2025.
I strongly suggest you consult with the Business Financial Manager, Funds Certifier, and/or Legal Office for additional guidance.