You have to wait for the new percentage to propagate to the main page. Its almost always this way. Click through to see the new discount. It's not really a borking, more just a fact of data propagation. It usually takes 5-10 mins for it to happen.
IE Trine 3 showed 15% on main page even though the Flash deal is 25%. I saw it immediately when I opened the store page (sometimes its slow there too) it only now shows 25% on the front page for me.
I refreshed a few times before your post - no update on store's main-page.
I just refreshed a few moments ago - things look to be in order now on the main store-front page.
Finally matching-up now.