How to get the previous value from string array c#(Unity)

I have this example data

Data: P ,B ,B ,T ,P

This must be something like this

But what is happening to me is this

here's my code

string[,] table = new string[104, 6];

string newPreviousValue = "placeholder";
int xIndex = -1;
int yIndex = 0;
if (result.Equals(newPreviousValue) &&  yIndex < table.GetLength(1) - 1)
{
    yIndex += 1;
    table[xIndex, yIndex] = result;
}

else

{
     xIndex += 1;
     yIndex = 0;
     table[xIndex, yIndex] = result;
}

So you won't get confuse the result variable is the data generator. What could be missing on my condition?

I tried doing something like this

if (result.Equals(newPreviousValue) && result.Equals(newPreviousValueTie) && yIndex < table.GetLength(1) - 1) but what's happening here is they're all in y axis falling in line .