@kendralala Computerized plagiarism checkers will flag all kinds of weird things. If you used a common phrase like “of the” too many times in a single document, that will be counted as not original.
If you writing on a technical topic such as quantum computing (something I wrote about in a post on Canada’s new Prime Minister) you might have to use very specific phrases, or even specific combinations of phrases, that the plagiarism checker will see as being “copied.”
In most cases, as long as there is no more than 15-25% similar/matching content, your work would be considered original. So if you got a score of 75% original, that’s right on target.