DSE decrements figures in interval ]1E12..1E13[ by 10, 0 expected. Found running ROM version C under Emu42, confirmed by JF Garnier on real version A and C machines.
Interesting, but with figures in interval ]1E12..1E13[ we are well above the maximum value for DSE specified in the HP-42S manual, which is 9999999, so I would not consider this a bug.