2-time-shovels ?

hi, i got 1 of my shovel from 15 coupons and the other from ASSASSIN BADGE (7 days), i don't know if both times for shovel mix and the total time increase or what?
cuz i dont want 2 shovels, (1 left for 20 days only, the other 6 days only).

idk if this is common in CF, i think CF should try to fix this, 2 limited time weapons, should be joined into single (resulting expanded time limit).