Font Size

I’m using Kirki’s stable version downloaded from “ww.wp.xz.cn” and the instructions provided by Sunny Johal here. So far, no problem until I attempt to change “font-size”.

As an example, this is a partial portion of my code:

$controls['theme_title_control'] = array(
        'name'       => 'theme_title_control',
        'title'      => 'Header Title Control',
        'tab'        => 'theme-header',
        'properties' => array(
                'selector'   => '.site-title a'
         ),
         'default' => array(
                'font_color' => '',
                'font_size'  => array( 'amount' => 4, 'unit' => 'em' ),
         ),
    );

As you will appreciate, I have set a default font size of 4em. When I open the Customizer and go to Appearance ==> Font Size, the 4em value appears and is applied. However, when I try to change this value with the slider, the slider erases the 4em value and gives me a value range from 10em to 100em. Hitting reset doesn’t bring the 4em value back. How can I change this behavior so that the range is 0.5em to 10em. Any guidance appreciated. Thanks!

https://ww.wp.xz.cn/plugins/kirki/