Accessing inflation layer from costmap_2d::Costmap2DROS

Hello When I access costmap_2d::Costmap2DROS.getCostmap().getCost(), which layer do I read from? When using the costmap arguement in the function makePlan() in the global planner of move_base, and reading with getCost(), the inflation values that are visible in Rviz are not represented in, costmap_2d::Costmap2DROS.getCostmap().getCost(). E.g. the cost around the obstacle is not gradually decreasing as you would expect. Any ideas how to solve it?