If an expanding central bank balance sheet means debasement, what does it mean when the balance sheet is shrinking? Because the opposite of "debasement" has be

If an expanding central bank balance sheet means debasement, what does it mean when the balance sheet is shrinking? Because the opposite of "debasement" has been happening for some time now. https://fred.stlouisfed.org/graph/fredgraph.png?g=1rdgN https://fred.stlouisfed.org/graph/fredgraph.png?g=1rdgN