While working with sitecore buckets, it is possible that you will encounter this warning on top of the item:
Unbucketable Item stored in an Item Bucket
This item is stored in an item bucket. However, it is not hidden because its template is not bucketable. If you want to hide this item in an item bucket, you must make the template that is based on bucketable
It could mean that either you have items in that bucket that are not bucketable or the current item itself is unbucketable but is placed inside a bucket item. For former, simply sync the item as shown in the screenshot below and for latter, select the parent bucket item, and try syncing it.