ScatterCtrl_Demo/Dynamic tries to update the plot every 5 ms.
Depending on the computer, compiler options (debug - release) and painting mode (Painter - Draw), the update is done faster or slower, and CPU load varies.
If you change line
SetTimeCallback(-5, THISBACK(Animate));
changing -5 (5 ms update) with 500 (500 ms update), probably your CPU load will be about 0%.