Fix Poor Wording and Poor Calculation of Dynamic Bundles
First of all, the Dynamic bundle price had already been applied by the time you see it on the store, but the wording says "You already own _ items in this bundle so their prices WILL BE deducted from your total." It should say "...HAVE BEEN deducted from your total." The other wording leads people to think there will still be a discount applied on the price they see, and they don't see the original price unless they log out.
Second, the way you calculated the discount is not ideal.
I think ideally it should subtract the amount you have already paid from the total: $60 bundle - 1 $30 game = $30 bundle.
Or if that's giving too much away, ignore those games and calculate the remaining at the same percentage: $80 original value (25% off). Remaining games total $50: 25% off = $37.50 bundle.
But the way you appear to be calculating (by my best guess) it is to take the discounted price of the owned games (25% of $30 = $22.50 ) and subtract it from the original value (80-22.50 = $57.50) and then discounting that by the discounted price: ($57.50 - 25% = $43.13 ) and then rounding up to the nearest $5 for a clean number so a $45 bundle. Keep in mind the original price was $50 so now instead of a 25% discount, it has been reduced to a 10% discount... Or worse, depending on the actual discount and prices.
I mean, good on you for including dynamic bundles at all, but that doesn't really motivate me to buy it when I'm only getting $5 off while the rest of the world gets $20 off.