✓ Accepted answer
Variables can only contain one value.
Here you are using an and operation, which will return a boolean data type.
With Roblox lua, as you have some instance found using script.Parent.Counter0 this will return true.
Your expression will probably be evaluating to true and true and true and true and true which is true, so shopManager.Counter would contain the value true rather than an object/instance.
You should probably use an array/dictionary in index these instead.
e.g. shopManager.counter = {script.Parent.Counter0, script.Parent.Counter1, script.Parent.Counter2, script.Parent.Counter3}
And to read these later on you would have to access a specific item in the array such as shopManager.counter[1]
This will probably be of help: https://developer.roblox.com/en-us/articles/Table