4.5 × 240 × 3840 × 2160 ≈ 9 GB/s
It seems markdown formatting ruined your numbers because of the asterisks. Whatever is written between two of those turns italic, so they’re not ideal for multiplication symbols here on Lemmy (or any other place that implements markdown formatting).
Try a session manager add-on. In the list view, it’s easier to close the irrelevant ones, then save the important ones under a meaningful name, never to be restored - but just knowing it’s there if needed brings peace to mind, at least for me.