Why "update" mode want to delete files in Right side?

[orzion]

Hi,
can you explain why update mode want to delete files in Right side?
i read the documentation https://freefilesync.org/manual.php?topic=synchronization-settings
"If you only want to add files to your backup, but never delete, then select the Update variant.
Files deleted on the source side will not cause file deletion on the backup drive (e.g. after you've made room for new photos on a digital camera). On the other hand, files deleted on the backup drive will not be copied over a second time (e.g. after you have removed photos you don't want to keep)."
so why he want to delete file.
please see me attachment.

[xCSxXenon]

If you hover over the icon in the middle, on the row containing these deletions, it will tell you why it wants to delete them. If they have been moved, it might be "moving" them by deleting and copying again

[Plerry]

It seems you have selected to use the "Use database file to detect changes" option (in the Synchronization Settings (F8) window) in your Update sync.
Then, as xCSxXenon replied, files that were moved in your source/left side will also be moved in your destination/right side (shown as a "Delete right item" action in the original right-side location and a "Copy new item to the right" action in the new location).

If you remove the checkmark in the "Use database file to detect changes" box, there should be no right-side deletions.
But then: if items have been moved in the source/left side, such items will be copied to their modified location (or their name changed to their new name), but will also be retained(= not deleted) in their old location (or under their old name).