Number of books on device shown in Calibre differs from the one shown on the Kobo

Hi,

:help:
I tried to find a solution on the forum, but couldn't find the thread, sorry for that.
I have 1519 books on my Kobo but when I plug it, Calibre shows only 1125 books on device.
If someone has an advice to solve this issue....:thumbsup:

Thanks