This error is saying that a variable is defined twice! Since one variable cannot have two different values, it errors out.
When you look at the area that lists the default variables for the affection bars is the variable "character1affection" in there twice? Each of the lines should have a different number so we don't have repeats! Check for "default character1affection = 20".
If you don't see any repeats, is it the case you have multiple different scripts in your game that can define this variable? Check to make sure any other scripts you've added don't define this variable either!
If all else fails, try deleting the .rpyc file in your game folder that has the same name as the script you added from this plugin, and run the game again!
Let me know if it works! Good luck!