prolongeth days = increaseth days; not necessarily in number, but in greater value and importance.
shortened = cut down, or made little, as in Isa_50:2; Isa_59:1. Mic_2:7. Num_11:23; Num_21:4. (discouraged). Jdg_10:16 (grieved); Pro_16:16 (vexed). Job_21:4 (troubled). Zec_11:8 (loathed). Psa_102:23, where it refers to affliction, not to continued living.