What instructions are you referring to? Do you have a link?
If you have deleted an image from the cloud using LrMobile, then it will no longer appear in All Synced Photographs (in LrC the cloud-deleted image is only "unsynced", so it stays in the LrC catalog but is removed from All Synced Photographs). It will also be removed from any synced collection that it may have been in.
The best way to delete images from the cloud which are also synced with LrC would be to just mark them as rejected in the cloud app, then revert to LrC and filter for the rejected images. Then you can either delete them from LrC (which also deletes them from the cloud) or just remove them from All Synced Photographs (if your intention is to remove from the cloud but retain in LrC).