try the following, to count the number of letters in a particular line(0)
[procedure TForm1.Button1Click(Sender: TObject);
var
a:Integer;
begin
a:=length(Memo1.Lines[0]);
label1.Caption:=IntToStr(a);
end;]
or to count the number of total letters (in fact characters)
[procedure TForm1.Button1Click(Sender: TObject);
var
a,b,c:Integer;
begin
a:=length(Memo1.Lines[0]);
label1.Caption:= IntToStr(length(Memo1.Lines.Text)) ;
end;]