Customs MIRO and MIGO

Hi,

I have entered the values of CVD and Customs duty during Customs MIRO as 100 USD for each line item and saved.

When i do MIGO,asked for commercial Invoice number,entered and saved.

When i see the FI documents,the each line item value varies from 100USD to 193.75 USD.

How this change happens and where should i correct?

Please reply.

Regards