The amount of the deposit required under Sec. 831.622 or Sec. 831.685 equals the sum of the monthly differences between the annuity paid to the retiree and the annuity that would have been paid if the additional annuity reduction elected under Sec. 831.622 or Sec. 831.685 had been in effect since the time of retirement, plus 24.5 percent of the increase in the designated base (computed as of the time of retirement) on which the survivor annuity is calculated. [51 FR 31935, Sept. 8, 1986, as amended at 58 FR 52881, Oct. 13, 1993. Redesignated and amended at 58 FR 52882, Oct. 13, 1993]