How to get the same random position for spawning rock in Endless Runner tutorial

I tried to follow the instruction that I found on this https://docs.unrealengine.com/latest/INT/Engine/Blueprints/UserGuide/RandomStreams/ link to get the same random position for spawning rock but it end up like this.


There is any way to make the rock spawn on random position and get the same outcome when we replayed it?