I think the 5% up day you are referring too, you actually mean BBUS should have gone ‘down’ 12% not ‘up’ as you mention. I think from memory the day before the S&P fell like 2-3% but the ASX was closed on that day, so BBUS had a catch up day.
Also, BBUS is based on Futures that trade all day long. S&P may close up or down 2-3% but Futures then may move in opposite direction. BBUS trades on real time data, not close of S&P price.
accumulating around $6.00. Big day moves, next leg down coming soon...