t(20)-5=15=o k(11)-5=6=f w(23)-5=18=r n(14)-5=9=i → ofri
Try backward: t(20) → r(18), k(11) → i(9), w(23) → u(21), n(14) → l(12) → riul — no.
Try instead: (i.e., code was shifted -1 from plaintext).
Actually, I’ll just give the most plausible decode: