I don't understand what you mean by different weights but the product consists of sandpaper of different grit sizes. That means it has fine paper more for polishing or fine sanding and also coarse. As described these are:
3x K40, 6x K80, 3x K120, 3x K180, Best for Paint, suitable for paint, varnish and filler: 2x K40, 2x K80, 4x K120, 2x K180. The K40 is a coarse grit and the K180 a fine grit, the others of course in between.
From my point of view it makes sense to buy this package, you will then quickly notice which ones you need frequently and which ones you do not. Some will then order them again and others won't...
I hope I was able to help.