I have two equations:

$
50.8 \lfloor \frac{w - 1}{50.8} \rfloor
$
and
$
25.4 \lfloor \frac{w - 1}{25.4} \rfloor
$

I need to determine if they are equal, how can I do this?

What I think the the first equation does is determine the nearest width to $w$ mm that will fit a whole inch but I cannot work out why the writer has used 50.8mm (2 inches) instead of 25.4mm (1 inch).