If you want to create a label with a 20mm inner circle, you will need to edit some registry keys. You can't do it from the software interface. Just go to Start, type regedit and open the utility. After that, navigate to HKEY-CURRENT-USER > Software > MediaNavigation > CDLabelPrint > 1.0 > Settings > SizeAdjust > .Standard CD (12cm), double click on Inner and change the value to -230. You need to multiply by -10 the difference between 43 and the inner circle diameter you want. In your case, (43 - 20) * (-10) = -230. After that, launch the software, click Adjust Circle Size, press OK without changing anything and print your label.