I used to do this stuff all the time I personally don't think it told me much about my hair (after all, these are considered rough estimates).
But, according to this test:
Hair sinking to the bottom = high porosity
Floating in the middle or so = normal porosity
Hair floating on top = low porosity
Keep in mind that porosity levels do vary around the head, so it's recommended to get a strand from some different areas in order to see a more clear picture. Again though, in my experience, I found out a lot more by just experimenting with moisturizing/conditioning ingredients etc. and seeing for myself how my hair takes to it. Best of luck!
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