感谢stillatmylinux的掌舵。

如果有人需要类似的东西，下面是我最后使用的代码

// Woocommerce Percentage Saved

function percentager_shortcode($atts)
{
// override default attributes with user attributes
$percentager_atts = shortcode_atts([
                                 \'reg\' => \'500\',
                                 \'sale\' => \'200\'
                             ], $atts);
                             $added_up = round( ( ( $percentager_atts[\'reg\'] - $percentager_atts[\'sale\'] ) / $percentager_atts[\'reg\'] ) * 100 );

// start output
$o = \'\';

// Words
$o .=  esc_html__($added_up, \'percentager\') . \'% Off\';

// return output
return $o;
}

function percentager_shortcodes_init()
{
add_shortcode(\'percentager\', \'percentager_shortcode\');
}

add_action(\'init\', \'percentager_shortcodes_init\');

[percentager reg=“{{meta:\\u regular\\u price}}}”sale=“{{{meta:\\u sale\\u price}}}}”]