White icon, green checkmark

Desktop client 3.6.2 for Windows
Nextcloud 24.0.4 as TrueNas plugin

everything seems alright but there’s a strange icon in windows explorer.
i’ve got icons for sinchronization like green icon, arrows icon, cloud icon etc…
in some folders I found a “reverse coloured” green icon, with white background and green checkmark.
what does it means? seems missing in official docs…