What's the criteria for the plagiarism in Nigeria?

The plagiarism test must be below 15%.

Whenever we use our personal plagiarism software, sometimes we score 0% but it’s shocking when we take the same thesis to the school plagiarism software, it scores higher than 15%..

I think it is because ours is free version and that’s why it is not as strong as the university version and they pay regularly to always update the software… that’s what I was told by the ICT personnel running the school plagiarism test