indentation looks strange again. Ignore if it's ok in your code.

you can omit the ';' after QDEBUG

10% error is a lot. Can you decrease it?

It is ok in code

Yes, I have decreased it to 1%. Is it ok?

The relative error should be as small as possible. Normally you should only have numerical errors. In your case the expected value has a limited number of digits which leads to a deviation from the calculated value. Try to reduce the error as much as possible.