These are index folders the presence of which can be quite annoying.
To locate them
find . -type d -name "@eaDir"
if you’re feeling ok about automatically deleting them then:
find . -type d -name "@eaDir" -print0 | xargs -0 rm -rf
On a Synology NAS you can disable feature as follows
synoservice --disable pkgctl-SynoFinder
warn: The runkey of service [pkgctl-SynoFinder] has been set to "No"