MEALS
T cannot be the last letter, because SHOOT was 0.
For MEANT and GIANT the only two letters in common were 3rd A and 4th N.
If 0, then N is fourth, because the only change (not including the T->S, which is already disproven) from MEANT to MEALS was N->L, meaning that N has to be fourth.
If 1, then A is third, because the only change from MEANT to MEALS (not including T->S) was N->L. As shown below:
MEANT
MEALS
If it has been striked, it was disproven before. Now, since the only change was N-> L and the score dropped, A has to be the right letter.