I know why.
Ok so either you attacked a monster in tzhaar than didnt kill it than went to wc. Than someone else went to tzhaar and finished off the monster you started to kill. They than killed it and you got the tickets instead of them.
Or some times with the npc random drop coding their is a bug and sometimes you get the drop instead of the person that killed the npc.
Thats the reason why you got 20 tickets, Its happened to me before but with tzok coins.