That's not that simple, you have to keep in mind that the current version by design as well as the populsion is basically the Russian P800, which also has a range of 290Km, so that is a limitation of the missile itself. Launched from an aircraft at high altitude will increase the range further, but Brahmos mini will actually be a more upgraded version, not only a smaller version. When you look at videos and interviews from Aero India this year, it was stated that we can develop a new propulsion for the smaller system, which than can be aimed on more ranger too, since we don't get it from Russia anymore, which are bound to international laws. Just like the Brahmos 2 is not limited to 290Km, since it's a complete new developmed missile, with the Russians as a development partner, but they are not selling us parts that would fall under international export laws.
However, the main advantage of Brahmos is speed and that will remain to be the priority and not range. Imo it's more a replacement of anti ship and land attack missiles like the Club S and not like a Tomahawk missile, which will be covered by Nirbhay.