You have the numbers reversed -- it's not that the Beatles is only 0.04% of your piece, the analogy is if you only copied 0.04% of the Beatles piece. Google only copied 0.04% of Oracle's source code.

The test for "fair use" is not only based on portion of original used. It is a four part test, where the weighting of the four parts is not specified, it's subjective (as are some of the parts).

1. Purpose and character of the copy (which mainly ends up meaning commercial vs non-commercial) 2. nature of the copyrighted work (which often ends up being about how "original" it was) 3. amount copied 4. effect on the market

https://fairuse.stanford.edu/overview/fair-use/four-factors/