The Originality Report provides a summary of matching or similar areas of text found in a submitted paper. Because Turnitin's database is so large, it is natural that every piece of work submitted for checking will have some degree of matching. If you have used quotes and have referenced correctly, for example, this will show as a match. The Similarity Score is simply a tool to alert your supervisor of possible problem areas which they can then review to determine if the match is acceptable.
The color of the report icon is linked to one of five tiers of the Similarity Index. This is based on the amount of matching text found by the repository comparison. The possible similarity index percentage ranges are linked to a corresponding color:
The right hand side of the report lists the amount of times your work has been found against articles in the Turnitin database. The percentage figure indicates how much of your work is similar or matches text found in a specific article. In this example, 9% of the thesis was matched against one internet source.
The boxed number is a navigation tool helping your supervisor locate matching text at various places within your thesis and ascertain author intent from the surrounding context. In this example, although 9% of the work matches one source, the first display of the match shows that it is both cited, refers to statistics and is a relatively small amount of text. All of which indicate appropriate use of reference material.