I did a report on this back in University. This was actually Pilsudki's plan during the 1919 War. Didn't really work out. The Poland of today is really odd because it's one of the MOST homogenous countries in Europe, when in the past it had always been a collection of many different poeples.
The Poland shown on the map (the darker area) is a lot more homogeneous than interwar Poland actually was, as like you say there were large Belarussian and Ukrainian minorities and smaller Lithuanian and German minorities.
The claimed areas on the map which actually have a Polish majority are Upper Silesia, southern East Prussia and parts of the Vilnius region and western Galicia.
Sorry I forgot to add: The claimed lands are divided up according to the country which administers them, showing how the rightful Polish lands have been shattered. Warmia, Masuria and Powiśla (southern East Prussia) and Upper Silesia are part of Germany, Gdańsk/Danzig is a LoN Free City, Galicia is independent, Cieszyn/Teschen, Orawa/Orava and northern Spisz/Spi are part of Czechoslovakia, Podalia and Volhynia is Ukrainian, Grodno/Hrodna and Minsk is part of the White Russian region of Russia and finally Vilnius and Suwałki is Lithuanian. The title hopefully says 'Reclaim the Stolen Lands' and actual Poland is labelled 'Free Poland'.