While the Color based water profiles in Bru'n Water are modestly mineralized profiles that are well-suited for ales, most lagers can actually benefit from less mineralization. However, 'less' does not mean none!
We have it from Dr. Narziss that PU does not use the raw tap water in Pilsen. They do mineralize the water somewhat and that mineralization does include gypsum. Unfortunately, we don't have details on the levels they take their mineralization. From other anecdotal evidence, it does seem that very modest mineralization is all that is necessary. On the order of 20 to 30 ppm calcium along with some chloride and sulfate tends to produce good lagers. That mineralization is primarily for flavor...the beer tastes better.
Since there are benefits in using a higher calcium content in the mashing water to help precipitate oxalate, the new supporter's version of Bru'n Water includes a setting that assumes that all of your sparging mineral additions are added directly to the mash tun in order to boost the Ca content. It does all the recalculation of the mash pH at the higher Ca and Mg levels and also reports the diluted levels of all the ions in the kettle (this assumes that the sparging water has no additional minerals). Since lager yeast performance is enhanced by reduced calcium content and there is less flavor from the low mineralized water, this setting provides the best of both worlds. Low mineralization in the kettle and higher mineralization in the mash for oxalate removal.