Extracted MTO/BOM from Report generation in MS Access Database include all component or some are missed/hide ?

Dear Bentley Family,

 When we extract the MTO/BOM from Report generation in MS Access Database, whether all component are included in that single database or some component/item are missed/hide ? , because when we cross-checked this extracted database by our actual(manually calculated) MTO, we are finding the differences in quantity.

Waiting for your earliest reply.

 Note - We are using:

Software :  Bentley Autoplant V8i - SS4 version : 8.11.9.140 , Autocad 2012-64Bit , Naviswork 2013 , Inventor Ultimate 2014-64 Bit , MS-Office 2010 - 64 Bit.

Hardware : Workstation Dell Precision T3600