Because it is getting a random integer each time you call the “Get” node. So first time it calls maybe chooses index 3 passes that to function. Then cruises along to your “print” node and the print node itself calls the “get” and maybe this time chooses index 2. If you want it to say the same thing, store the first output as a variable. See this video, I helped someone else with this very issue a while back. May clear things up 
