Case Clicker how to edit the code values for higher rarity draws, help?

I and my friend wanted to play this case clicker game but it was getting boring. We grabbed a UNCOPYLOCKED version of it and started playing it by ourselves, but we wanted to add our own cases so we can make it more challenging since it only came with 4 cases one including the cost of Robux. I went into the code and sat there for about 45 minutes trying to figure out what all the variables and compacted scripting did. I finally found how the script draws random values but I don't understand what I have to change to make my own case and increase the chances of getting a higher value item. No matter how many times I changed the value of the random draws it doesn't change a thing. Someone, please help.

https://pastebin.com/wgFqvVDz -- Code from the script.