i am using Flutter Syncfusion Date Picker i want to give circular border radius in Special date decoration property but it not give desired result

Question

 Center(
              child: Container(
                // height: size.height * 0.300,
                //  width: size.width * 0.30,
                //height: 321,
                width: 308,
                decoration: BoxDecoration(
                  borderRadius: BorderRadius.circular(20),
                  boxShadow: [
                    BoxShadow(
                        color: AppColors.greyColor,
                        blurRadius: 3,
                        spreadRadius: 5,
                        offset: Offset(0, 0)),
                    BoxShadow(
                        color: AppColors.greyColor,
                        blurRadius: 5,
                        spreadRadius: 1,
                        offset: Offset(5, 5)),
                  ],
                ),
                child: MySfDateRangePicker(
                  view: DateRangePickerView.month,
                  headerStyle: DateRangePickerHeaderStyle(
                      textStyle: TextStyle(
                          fontFamily: 'Nunito',
                          color: AppColors.primaryDarkBlue,
                          fontWeight: FontWeight.bold,
                          fontSize: 13)),
                  maxDate: DateTime.now(),
                  // maxDate: DateTime(2024, 03, 25, 10, 0, 0),
                  rangeTextStyle: TextStyle(
                      color: AppColors.primaryDarkBlue,
                      fontFamily: 'Nunito',
                      fontSize: 14),
                  startRangeSelectionColor: AppColors.gradientOrange2,
                  todayHighlightColor: AppColors.primaryDarkBlue,
                  endRangeSelectionColor: AppColors.gradientOrange2,
                  backgroundColor: AppColors.white,

                  /// For Single Selection Mulligan Dates Initial
                  initialSelectedDates: [
                    DateTime(2023, 12, 01),
                    DateTime(2023, 12, 15),
                  ],

                  /// Display Date Ranges Initial
                  initialSelectedRanges: controllerr.initialRanges,
                  minDate: DateTime(1999),
                  rangeSelectionColor: AppColors.scoreRange2,
                  selectionMode: DateRangePickerSelectionMode.multiRange,
                  selectionColor: AppColors.primaryColor,
                  selectionRadius: 20,
                  monthViewSettings: DateRangePickerMonthViewSettings(
                      specialDates: controllerr.mulliganDates,
                      showTrailingAndLeadingDates: true,
                      dayFormat: 'EEE',
                      viewHeaderStyle: DateRangePickerViewHeaderStyle(
                          textStyle: TextStyle(
                              color: AppColors.darkGreyFontColor,
                              fontFamily: 'Nunito',
                              fontSize: 11,
                              fontWeight: FontWeight.bold))),
                  monthCellStyle: DateRangePickerMonthCellStyle(
                    textStyle: TextStyle(
                        color: AppColors.primaryDarkBlue,
                        fontFamily: 'Nunito',
                        fontSize: 14),
                    specialDatesDecoration: BoxDecoration(
                      color: AppColors.gradientDarkBlue,
                      shape: BoxShape.circle,
                      gradient: LinearGradient(
                        begin: Alignment.topLeft,
                        end: Alignment.bottomRight,
                        stops: [0.0, 0.7, 1.0],
                        colors: [
                          Colors.grey[300]!, // Light grey start color
                          Colors.blue[900]!, // Dark blue middle color
                          Colors.blue[900]!, // Dark blue end color
                        ],
                      ),
                    ),
                    cellDecoration: const BoxDecoration(shape: BoxShape.circle),
                    specialDatesTextStyle: const TextStyle(
                        color: Colors.white,
                        fontFamily: 'Nunito',
                        fontSize: 14),
                  ),
                ),
              ),
            ),

i want to give border radius 15 to special date decoration and but it not minimize as axpected. in blue color is special date