tickOffset property
Adjust the space around ticks in the SfSlider,
SfRangeSlider, and SfRangeSelector.
The default value is null.
This snippet shows how to set tick offset in SfRangeSliderThemeData.
SfRangeValues _values = SfRangeValues(4.0, 8.0);
Scaffold(
    body: Center(
        child: SfRangeSliderTheme(
            data: SfRangeSliderThemeData(
                tickOffset: Offset(0.0, 10.0),
            ),
            child:  SfRangeSlider(
                min: 2.0,
                max: 10.0,
                interval: 2,
                minorTicksPerInterval: 1,
                showTicks: true,
                values: _values,
                onChanged: (SfRangeValues newValues){
                    setState(() {
                        _values = newValues;
                    });
                },
           )
       ),
   )
)
Implementation
final Offset? tickOffset;