I just released 1.1.0 which has limited template support.
copy the file wp-content/plugins/soft79-wc-pricing-rules/templates/single-product/bulk-rule.php
I commented an example on how to calculate the discount percentage:
$discount_perc = round( ( $row["price"] - $product->get_price() ) * 100 / $product->get_price() ) . ' %';
$discount_perc and you’re good to go.