The Originality Score shows you what percentage of your document matches with documents in the Ephorus database. The more similarities there are, the lower your score will be.
If you have a score of 60%, this means that 40% of your content is unoriginal and is found in the Ephorus database. This doesn’t necessarily mean that this 40% is plagiarism. This depends on the way you’ve quoted or paraphrased and if you cited your sources the right way.