Code (Text):

1. command /multi <player> <integer> <integer>:
2.     trigger:
3.         set {multi::%arg-1's uuid%::amount} to arg-2
4.         set {multi::%arg-1's uuid%::left} to arg-3
5.  
6. on left click on yellow wool:
7.     if {multi::%player's uuid%::amount} is set:
8.         if {multi::%player's uuid%::left} is more than 0:
9.             remove 1 from {multi::%player's uuid%::left}
10.             set {punch::%player's uuid%} to {punch::%player's uuid%} * {multi::%arg-1's uuid%::amount}
11.         else:
12.             delete {multi::%arg-1's uuid%::*}
13.             add 1 to {punch::%player's uuid%}
14.     else:
15.         add 1 to {punch::%player's uuid%}

Command usage: /multi <player> <multiplier amount> <punches until it runs out>
e. g.: /multi Minecoll_YT 2 20 (it would give me 2x the points for 20 punches)