Current GS-13 here and still have my USAJOBs account active. If you are applying and haven't separated from active duty yet and its your initial active duty tour, this appears to be a requirement in lieu of the DD-214 since you won't necessarily have one yet. I copied and pasted the full requirement that I found on a similar job posting: ACTIVE DUTY SERVICE MEMBERS: The VOW Act requires federal agencies to treat an eligible active duty service member as a veteran, disabled veteran, and preference eligible (as applicable) when applying for civil service positions before the effective release or discharge date. Appointment of military members before the release or discharge date is permissible if the member is on terminal leave. At the time the active duty member applies for a civil position, he or she must submit a "certification" memo in lieu of a DD-Form 214, Certificate of Release or Discharge from Active Duty. Active duty members applying for a civil service position without submitting a valid certification memo or DD-Form 214 with their application will render the member ineligible for the position. The certification memo must originate from the member's military service branch on official letterhead and contain the following:
Name/Rank/Grade of Service Member
Branch of Armed Forces
Dates of Active Service (Start and End Date(s)
Expected Date of Discharge/Release from Active Duty
Terminal leave start date (if applicable)
Expected character of service (honorable or general) and type of separation (i.e. separation or retirement)
Must be certified within 120 days of anticipated discharge
Signature by, or by direction of the adjutant, personnel office, unit commander, or higher headquarters commander.
Note: The VOW Act provides tentative preference. If appointed, a DD Form-214 must be submitted upon receipt.
My recommendation: draft up the MFR with all the details as listed above and have your unit commander sign it. Then, upload to your docs and the application.