For historical analysis, how does Pralana know whether my asset classes are stocks, bonds, etc.

When you create asset classes, there doesn't appear to be a way to designate an asset class as, for example "stocks" or "bonds" (aside from the choice of asset class name). When the historical analysis is run, does Pralana treat all of asset classes as the same when it's applying historical rates of return and apply a sort of blended rate to them? Or did I miss an input somewhere where I should be mapping my custom asset classes to standard ones?