What's Kx of LT8601?

Hi

I don't understand what Kx means.  In page 14 inductor selection of LT8601 data sheet, Kx is suddenly appeared.

Why are K1 = 1.7, K2 = 1.0 and K3 = 1.4 selected ? Could you please let me know how to calculate the Kx values ?

Regards,

Hiroyuki