Section 294. Redemption

The  sinking  fund bonds to be redeemed from the
  general  sinking  fund  or  any  additional  sinking  funds  established
  pursuant  to  section  two  hundred ninety-eight may be selected in such
  manner as the comptroller may determine and may  be  identified  on  the
  face  thereof. The principal amount of sinking fund bonds required to be
  redeemed on any date by payment from the general  sinking  fund  or  any
  additional  sinking fund shall be reduced by the principal amount of any
  such bonds which has been timely purchased or redeemed and cancelled  by
  the   city  and  not  theretofore  applied  as  a  credit  against  such
  requirements.