Well funny how i am getting downvoted every now and then for just showing what I found.
yes the other language is german. I dont 't know if that shows in english language version as well. That is a normal thing for PTR that some parts of the game are not translated yet. In this case the 6 piece bonus of SWK had a placeholder in the old PTR patch which they now replaced for testing. It is possible that the set bonus should point to the translated version of the new 6 peice SWK, but due to a bug it points to this bonus instead.
Maybe someone with a german client can confirm this. I was also showing on the SWK legs.
Obvoiusly the bonus is on the wrong set and totally broken in that state. 100% dmg reduction is 0 dmg as in invincible. Why would i fak something like that which is obvisouly totally wrong and broken? However if actually added to a Zuni set I believe it will say 5% per Fetish. With 15 fetishes from passive and up to 8 fetishes from fetish army you would get: 0.9523 = 0,307 which would be a dmg reduction of about 69% at max 23 fetishes.
1 fetish: 5%
2 fetishes ~10%
3 fetishes ~14%
4 fetishes ~18%
5 fetishes ~22%
6 fetishes ~26%
7 fetishes ~30%
8 fetishes ~34%
9 fetishes ~37%
10 fetishes ~40%
11 fetishes ~43%
12 fetishes ~46%
13 fetishes ~49%
14 fetishes ~52%
15 fetishes ~54%
16 fetishes ~56%
17 fetishes ~58%
18 fetishes ~60%
19 fetishes ~62%
20 fetishes ~64%
21 fetishes ~66%
22 fetishes ~68%
23 fetishes ~69%
Just for info the In-Geom legendary power was shoing something different in german in the prrevious PTR patch as well. I dont't have one right now, but it was reading:
"Reduce the cooldown of all skills by 1 sec, whenever you use a cooldown spell" (In german). However the english client was showing "Reduce cooldown by 4-6 sec"