I want to change the length of the wordpress music player.

Thank you for your continuous support.
We are currently creating a site with wordpress.

I'd like to change the width of the sound source playback part in the picture below, but which file is it managed by?

Actual Screen

Source

I'm sorry that the sauce is too hot.
The theme type is relia.
Thank you.
If the element.style is set to 50%, the part of the black bar will be halved as intended...