While that is outside the scope of support, I could point you in the right direction with the understanding that it would ultimately be your responsibility to take it from here.
First, please setup a Child theme.
Then copy the code provided here to your child theme's functions.php file. (don't include the
<?php tag on the top of that code, it will break your functions.php file)
then see the line:
case 'variable': in the code, there is a Select options in there, that is the string that you want to change.