ASTM E1300 X6. Approximate Maximum Surface Stress

[Mat.]

Regarding Appendix X6 in the ASTM E1300, does anyone know where more information can be found on the variables k and n. I ask because in this appendix they refer to n as 16 for annealed glass, but what about HS and FT? Also, k, the surface flaw parameter has no given value or units or mentioned else where at all.

I also don't see how this equation produces a stress in terms of psi or psf as none of the variables include force. See below for the snip of the equation and its variables:

Does anyone have any experience using this equation? Any info is much appreciated.

Thanks.