Multi-phase RF ablation employing a two-dimensional or three-dimensional electrode array produces a multitude of currents paths on the surface of the ablation zone. The banknote can further swivel about one of the points to align the note with a desired path. The device comprises a visual representation of the variation range as a linear continuum, a continuum divider for visually dividing the continuum at user selectable points therealong, the points corresponding to values of the parameter, thereby to define regions therebetween and a category definer for defining categories for association with the regions.