One basis point is defined to be 0.01 percentage points. Therefore, a change of 0.21% could also be expressed as a change by 21 "basis points."
Basis Point
See also
Percentage PointExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Basis Point." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BasisPoint.html