This better not be the only thing on this planet that produces electricity, with only 12 charges remaining on it? But calling it 'lightning-aspected damage' suggests that it's better-known than that.
All right, let's try this with probe one clamped to sensitive Carissa area one, probe two clamped to sensitive Carissa area two, spend one charge, and immediately with no warmup turn up the intensity from zero to two-thirds of maximum.
(Obviously any linear slide like this one will control output logarithmically so that the just-noticeable-difference corresponds to the same interval at all points on the scale, Keltham knows and does not think to question; he's not thinking that he's setting the output to two-thirds of maximum output. Which, in fact, he is.)