TChart zoom peoblem ( BUG??)

Hi,
I'm having a little problem with the
ZoomPercent method of the TChart
component.
It doesn't seem to zoom in or zoom out very well.

Quote
Here's what i wrote:

procedure Button.Onclick.........
begin
    Chat1.ZoomPercent (100 + StrToInt (Edit1.Text) ); // to zoom in
     ............
........

procedure Button2.Onclick..........
begin
     Chart.ZoomPercent (100 - StrToInt (Edit1.Text) ); // to zoom out
     .......
.........

Problem ?
         The zoom in seems to zoom 4 times more then it should.

TIA
Jean-Francois