It may happen that the Unread count for a folder is greater than actual number of unread documents in that folder. Or the count of unread documents for a folder is shown as not null, when, in fact, it is.

Solution for Notes 6.x and 7.x:
1. Open to a view containing all documents.
2. From the menu select View > Show > Unread only.
3. From the menu select Edit > Select All.
4. On the action bar select the Folder > Move to Folder.
5. Select the Create New Folder button. Call the new folder “Unread”. Select OK to close the name dialog.
6. Select the Add button to add the selected documents to the newly reated Unread folder.
7. From the men select Edit > Unread Marks > Mark All Read.
8. Close and then re-open the database.
9. Switch to the Unread folder.
10. From the menu select Edit > Select All, and then Edit > Unread Marks > Mark Selected Unread. Note: DO NOT use the Mark All Unread option or this step.
11. Once the documents appear as expected then you can remove the folder by highlighting the folder and selecting from the menu: Actions > Folder options > Remove Folder.

If this does not work:

First, open the Trash folder and mark any documents in it as Read, then empty the Trash.
Then, purge the deletion stubs as follows:
1. Select File > Replication > Settings > Space Savers.
2. Set the “Remove documents not modified in the last XX” days to 0. Do not enable/select the property’s checkbox.
3. Close and re-open the database.
If purging the deletion stubs does not result in a corrected unread count or trigger the unread counts to be updated as expected when deleting additional documents, then create a new replica of the database.
– Simply marking the documents in the Trash folder as Read will not actually resolve this issue – it is only a temporary workaround.
– Workarounds involving marking all documents as read, and then optionally marking selected documents as unread, are not applicable to the folder unread count issue described in this technote.
The following workarounds, though likely less desirable, may warrant consideration in some cases:
Disable soft deletions for the database
Disable the unread mark count feature for folders in the outline. For more information refer to the document, “How to enable or disable the unread count for folders” (#1087629).