Thanks for sending us the screenshot. The problem is that the fixed product discount works per-product, so a discount for a single product will never be more than the product price.
What you could do is use this plugin: https://nl.wordpress.org/plugins/soft79-wc-pricing-rules/ and set this price rule for the products:
From: 10, To: 10, Price: -25%
You can do this either on the product page for every product to which it should apply or by using ‘WooCommerce’ > ‘Pricing Rules’ and create a rule for one or more products or categories.