Renka(1 hit) has 120% proration, so it's better to do that in a long combo. Take 214B>41236C>623AA>falling C combo for example. If you did 214B(1hit) here instead of 2, the damage overall would be 6011, whereas doing 2 hits of 214B would end up with the combo doing 5458 total...not to mention 214B(2 hits)>41236C won't even connect fully unless in the corner anyways, and you'd still be doing more damage with 1 hit 214B. 2 hits with 214B is really only for short combos using little magatama, but in bigger ones involving 41236C for example, you'd do 1 hit.