Dear Sahitya-san,
I think you found an error in our user guide. It has the wrong formula at this place. Because I'm not the author of the guide I'd need some time to work on the correct formula.
In the mean time please have a look at following…
Dear Gaurang,
Thank you for evaluating this power design.
The isolation depends exclusively on the PCB parameters. These are given by your own PCB design and by the physical dimensions of the coil. To support your requirements you can remove the negative…