Fret Layout ?

Hi All

I have a question about fret layout, if you use a ruler to layout the frets, how do you get these dimensions using the ruler?

In other words how do you mark the .0548 for fret #1 and so on, using the ruler?

Fret layout for a 28 VSL

Fret #1 3.0548 in or 77.593 mm

Fret #2 5.7764 in or 146.720 mm

Fret #3 7.0237 in or 178.402 mm

Fret #4 9.3122 in or 236.531 mm

And so on.

The other fretboard I made, I just copied the layout from another one, it was a 27 VSL, but now I need to layout a 28 VSLfretboard

Thanks

Ron