Service tax_ small service providers exemption

Dear Professionals,

I am really not able to comprehend this condition relating Small Service Providers Exemption ( notification 6/2005 ST dated 01.03.2005)

the provider of taxable service who starts availing exemption under this notification shall be required to pay an amount equivalent to the CENVAT credit taken by him, if any, in respect of such inputs lying in stock or in process on the date on which the provider of taxable service starts availing exemption under this notification;

Can anyone pls explain this condition with a practical illustration

Thanks in advance

Do we really need to pay the Cenvat amount or just reverse the entry???