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Do i have to fill out all 3 properties

No, but it is reccomended. If you do not fill them out, they will have a default value.

The default values are fairly amusing.

If you do not fill out the score value, the plugin will default to 100

What format should the score value be in

The score should be an integer between 0 and 100. It will ultimately come out as a percentage. The score does not need a % sign following it. Adding one will make the sky fall on your head

The score gets messed up! Help

This is probably because you added a % (percent) sign to the end of the score property. All you need to input is a number