The video quota only takes into account the size of <x id="START_TAG_STRONG" ctype="x-strong" equiv-text="<strong>"/>uploaded<x id="CLOSE_TAG_STRONG" ctype="x-strong" equiv-text="</strong>"/> videos, not transcoded files or user export archives (which may contain video files).
This is an <x id="START_TAG_STRONG" ctype="x-strong" equiv-text="<strong>"/>import<x id="CLOSE_TAG_STRONG" ctype="x-strong" equiv-text="</strong>"/> tool and not a migration tool. It's the reason why data (like channels or videos) is duplicated and not moved from your previous PeerTube website.
This is just an extra information injected in PeerTube HTML that is required by Twitter/X. If you don't have a Twitter/X account, just leave the default value.