Plot sprite from a string array on screen location

Hi, Apologies if this question is reappearing as I cannot find where my original question is.

From the question below you will understand that i am very new to UNITY :)

I have a string array

 "BBBBBBBBBB", 
 "BPPPPPPPPB", 
 "BP000000PB", 
 "BP000000PB", 
 "BPPPPPPPPB", 
 "BBBBBBBBBB";

The purpose is that it will plot a border sprite if it see a "B" , a padding sprite if it sees a "P" and nothing if it is zero.

 private void DrawBoundrySprites()
     {
         Vector3 pos = Vector3.zero;
         for (int r = 0; r < grid.Length; r++)
         {
             for (int c = 0; c < grid[r].Length; c++)
             {
                 pos = new Vector3(c, pos.y, pos.z);
                 if (grid[r][c] == "B")
                 {
                     Instantiate(borderTree, pos, Quaternion.identity, objWorld);
                 }
                 else if(grid[r][c] == "P")
                 {
                     Instantiate(padding, pos, Quaternion.identity, objWorld);
                 }
             }
             pos = new Vector3(0, r, pos.z);
         }

DrawBoundrySprites function works fine but its pos variable starts from bottom up. Meaning, the fist line of "B"s in array draws at lower end of the screen.

And if I change the two lines of Instantiate code as follows (as part of trouble shooting):

 if(r==0) Instantiate(borderTree, pos, Quaternion.identity, objWorld);

 if(r==1) Instantiate(padding, pos, Quaternion.identity, objWorld);

both Sprites for borderTree and padding are drawn on top of each other.

I have faint idea that it may be because of how unity divides its screen coordinates but am unable to pin-point the issue.