Hello,
You should enter values between zero and 100, with zero being unshaded and 100% being fully shaded. You can find more details in SAM's Help system (click the Help button in the Edit Shading Data window).
If you continue having trouble, please [url=mailto:sam.support@nrel.gov?subject=PV%20Shading%20Files%20from%20Support%20Forum t=_self]email me your files[/url], and I'll try to help.
Best regards,
Paul.