Case TS000844486 on IBM Support
Files less than 40KB in size is not considered technically as an "attachment" on Domino and stores it on the Body item.
When Notes opens this document, it recognizes that it cannot render these small items as inline data, so it automatically converts them to attachments. iNotes does not do this and that's why it only shows 12 of the 15 attachments; iNotes should take the same action as Notes.
The attachment handling in iNotes depends on $FILE and some @functions. If $FILE and @functions don't provide the attachment information, there is no way for iNotes to be aware of the attachment in the current architecture. In order to get all of the problematic attachments information in iNotes, Domino core side change is required. But, according to Domino development's response, iNotes is requested to handle them. It requires to implement a brand new framework and mechanism in iNotes. It is obviously a new feature enhancement, and it requires huge and risky change.