CSS has various units like px, %, EM or REM for expressing a length and each of them is suitable for its conditions.
In Jupiter you can change the CSS units for the CSS properties that takes length values for Customizer.
In order to change the CSS length unit in Customizer follow the steps below:
1. From the WordPress left dashboard menu, go to Appearance > Customize.
2. Select an element you want to change the styles for like Title Bar.
3. In Style tab, select the Customize for which element you want to change its styles.
4. Any CSS properties that takes length values such as margin, padding, font-size, etc. has an option for changing the units. If you click on the default unit, you can see the other options.
5. Select your preferable unit and type in the value.
Note: If you want to learn about changing the units for CSS properties in Elementor, you can refer to this article.