DoD: One mistaken click won’t force you into the new retirement system

Don't trust finance, check, re-check, and triple check everything. It's not that I think they are trying to trick you. But, nobody cares about your check more than you.
I never took the voluntary REDUX at 15 years. When I retired my checks were at REDUX rates. Come to find out it was because of a check mark on a form filled out by the retirement section. It got straightened out, but I would still be getting paid reduced checks if I had not been on top of it.
Check, re-check, and triple check EVERYTHING.