Unfortunately, for this particular promotion, Loews is keeping their collective lips sealed. The link in the email goes to this page:
http://www.loewshotels.com/?chebs=email_3046065_vv_ss_en_yf_summerofloews_05302012
And as you can see for yourself, there is zero information about the one-day sale other than a countdown clock.
Nevertheless, we wanted to bring it to your attention just in case you are about to book your stay at Universal. It is worth noting that, if you take advantage of a discount rate directly through Loews, you will not be able to book a Universal vacation package. The good news is that you can still get Early Park Admission to the Wizarding World and unlimited Express Pass access. However, you will not be able to book the Harry Potter breakfast or the new Universal dining experiences.