There is no default or custom report to list attachments by size.
Workaround:
If you want to see the individual attachment names based on size, you can click the details of Blocked Attachments.
Before opening the blocked attachments view, it need to configure the blocked file size.
Steps:
1.Open Advanced Configuration Options and configure blocked files under the SharePoint tab.
2. Set the maximum file size in MB you want to filter out. An example would be 10mb
3. Scan the database again and click the Blocked Files link.
4. This should list the attachment name and size.
