atoi not working inside of loop

[gobotsoup]

Hello, when I take the loop away the atoi call works fine. But when the for loop is wrapped around the atoi call, it seems like the char array goes out of scope or something and I do not get an int returned from the atoi call.

for(int j=0; j<length; j+=4)
{
 char Num[2];
 Num[0] = Buffer[j];
 Num[1] = Buffer[j+1];
 int num = atoi(Num);
}
length *= 4;