How can I change the font-size of heading in Apexchart in my Filament project?

$chartTitle = static::$heading;
return [
            'series' => $series,
            'chart' => [
                'type' => 'line',
                'height' => 300,
            ],
            'xaxis' => [
                'categories' => $xAxisCategories,
                'labels' => [
                    'style' => [
                        'colors' => '#9ca3af',
                        'fontWeight' => 600,
                    ],
                ],
            ],
            'yaxis' => [
                'labels' => [
                    'style' => [
                        'colors' => '#9ca3af',
                        'fontWeight' => 600,
                    ],
                ],
            ],
            'colors' => ['#ffc107'],
            'stroke' => [
                'curve' => 'smooth',
            ],
            'title'=> [
                'text'=> $chartTitle,
                'align'=> 'left',
                'margin'=> 10,
                'offsetX'=> 0,
                'offsetY'=> 0,
                'floating'=> false,
                'style'=> [
                  'fontSize'=>  '12px',
                  'fontWeight'=>  'bold',
                  'fontFamily'=>  'undefined',
                  'color'=>  '#263238'
                ],
            ]
        ];