Who ever took that 28m is shorting by 8m so far.....there is your culprit!
https://www.shortman.com.au/stock?q=SXY
Date Gross shorts 1 Issued capital % Capital shorted 2 Trade volume 3 Shorts as % of volume 4
Thu 6th Dec, 2018 573,818 1,452,999,535 0.03% 1,821,916 31.50%
Wed 5th Dec, 2018 1,005,102 1,452,999,535 0.06% 3,258,245 30.85%
Tue 4th Dec, 2018 818,107 1,452,999,535 0.05% 2,975,025 27.50%
Mon 3rd Dec, 2018 635,217 1,452,999,535 0.04% 4,888,883 12.99%
Fri 30th Nov, 2018 8,081,424 1,452,999,535 0.55% 28,046,340 28.81%
Thu 29th Nov, 2018 1,044,595 1,452,999,535 0.07%