sizeByAbsoluteValue property
When this is true, the absolute value of z determines the size
of the bubble. This means that with the default zThreshold of
0, a bubble of value -1 will have the same size as a bubble of
value 1, while a bubble of value 0 will have a smaller size
according to minSize.
API Docs: https://api.highcharts.com/highcharts/series.mapbubble.sizeByAbsoluteValue
Implementation
bool? sizeByAbsoluteValue;