In cell E6 (where you would place your new ETS), you must place your 16th year cutoff date. (You put in a date past that date)
You can only be paid a C Zone bonus through your 16th year of active service (based on your BASD). This is law, not Army policy.
AR 601-280, Army Retention Program, Chapter 5:
g. ZONE C eligibility—To be eligible for a Zone C SRB, besides meeting the qualifications of b above, a Soldier must—
(1) (POL MSG 08-01) Have completed at least 10 but not more than 14 years of active duty service on the date of reenlistment.
(2) Reenlist in the Active Army for at least 3 years.
(3) Have a total of at least 14 years of active service when the term of reenlistment is added to existing service.
(4) Have not previously received a Zone C SRB.
Note. A SRB will not be paid for any active Federal service beyond 16 years.