cant clear rubble with nere

[Aupo]

im using 1 barrel, 3 powders and 1 bomb to spark it all and no matter what, rubble have around 10 hp in end. in my first play i did with less and got it done but now i cant get there.

[arikel.pv]

Got the same issue in my last walkthrough - previous times managed to blow it up from the first try, too. Just do it in two steps, keeping in mind minimum amount of damage needed (22, if I remember correctly).