After you delete an image or collection from Lightroom mobile, the image or collection displays as synced in Lightroom.

While the image or collection appears to be synced, the number of synced photos is different between Lightroom and Lightroom mobile.

Solution

Photos that are deleted from Lightroom mobile are not deleted from the cloud. Therefore, the number of synced photos could be different between Lightroom and Lightroom mobile. Use this workaround to remove the images or collection from the cloud, and coordinate the data between the two applications.

1. In Lightroom, select All Synced Photographs in the Catalog panel in the Library module.
2. Select all the photos in this group that are not currently part of a synced collection. These images are the ones that you've deleted from Lightroom mobile, but that are still showing as synced in Lightroom.
3. Add these photos to any synced collection.
4. Delete these photos from that synced collection.