Ошибка: list index out of bounds -1

unit Unit2;
 
interface
 
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Grids;
 
type
  TForm2 = class(TForm)
    StringGrid1: TStringGrid;
    StringGrid2: TStringGrid;
    StringGrid3: TStringGrid;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form2: TForm2;
 
implementation
 
{$R *.dfm}
 
procedure TForm2.Button1Click(Sender: TObject);
var
  A: array [0 .. 4, 0 .. 4] of real;
  B: array [0 .. 4] of real;
  i, j: byte;
begin
  begin
    for i := 0 to StringGrid1.RowCount-1 do
      for j := 0 to StringGrid1.ColCount-1 do
         A[i, j]:=strtofloat( StringGrid1.Cells[i-1, j-1]);
  end;
  begin
    for i := 0 to StringGrid2.RowCount-1 do
     B[i]:=strtofloat(StringGrid2.Cells[0, j]);
  end;
end;
 
procedure TForm2.FormCreate(Sender: TObject);
var
  i, j: byte;
begin
  with StringGrid1 do
  begin
    fixedrows := 0;
    fixedcols := 0;
    rowcount := 4;
    colcount := 4;
    defaultcolwidth := 50;
  end;
  with StringGrid2 do
  begin
    fixedrows := 0;
    fixedcols := 0;
    rowcount := 4;
    colcount := 1;
    defaultcolwidth := 50;
  end;
  with StringGrid3 do
  begin
    fixedrows := 0;
    fixedcols := 1;
    defaultcolwidth := 50;
    rowcount := 4;
    colcount := 2;
    for i := 1 to 4 do
      Cells[0, i - 1] := 'X' + inttostr(i);
  end;
end;
 
end.

procedure TForm2.Button1Click(Sender: TObject);
var
  A: array [0 .. 4, 0 .. 4] of real;
  B: array [0 .. 4] of real;
  i, j: byte;
begin
for i := 0 to StringGrid1.RowCount-1 do
for j := 0 to StringGrid1.ColCount-1 do
A[i, j]:=strtofloat( StringGrid1.Cells[j-1,i-1]);
  end;
  begin
    for i := 0 to StringGrid2.RowCount-1 do
     B[i]:=strtofloat(StringGrid2.Cells[0, i]);
  end;
end;