rolls=: 4 5 5 5 0 10 2 3 4 5 4  5  4  5  10 5  5  4  5
shouldbe =: +/ 9   10  12   5   9   9   9  20  14  9
sfx =:  0   2   4    6   8   10    12    14 15    17
fx=: 13 : '(2*i.2%~(20<.+/1+10=y)){(1+10=y)#i.#y'
sf=: 13 : '(y+1|.!.0 y)+(2|.!.0 y)*9<y+1|.!.0 y'
sc=: [:+/fx{sf