The code you posted is taking the percentage ratio between the width of a certain component and the width of the whole page and the height of the same component with the height of the whole page, but it only gets the smaller proportion between the two calculated to consider whether the page is in landscape or portrait layout.
Apparently this number resulting from this line you posted is to be used for you to be able to calculate the value you want to get given the change in the default screen you used to draw. Assuming the canvas you are drawing the default layout on is 1024px by 768px, we would do it like this:
var scale = Math.min(
availableWidth / /*1024px*/
contentWidth, /*500px => (100 / 2048) = 48.82% of available height */
availableHeight / /*768px/*
contentHeight /*145px (100 / 5.2965) = 19.02% of available height*/
);
In this case your line would bring 19.02%, because the Math.min method brings the smallest of the array. So you would use the height of this object as a reference to determine its width too, in order to try to maintain the aspect ratio of the page. But the ideal thing, in my opinion, is that you learn to deal with flex layout, maybe even with bootstrap, to build responsive grids with less work, since the CSS will scale for you according to the screen size natively , without the need for calculations.
;D