For the series in which a corporate action (CA) has occurred in the underlying Security Option, [modifier_c] (change serial number) of the answer (DA124) to DQ124 (Request for acquiring instrument series) will be updated as 1, 2, 3..., and [ins_id_s] (issue abbreviation) will be updated as A, B, C....
For details, please refer to “4.7.1.2 Series Information associated with Corporate Action (CA) at the Underlying Level” of "J-GATE3.0_Connectivity_Manual_Commonalities_part".