These are the concentrated liquid form of the Calcium and Alkalinity traditional ESV 2 part solution. The instructions on the buckets explain how much RO/DI water to add to 'reconstitute' the solution to full strength. ESV sells them this way (concentrated) to save the customer shipping costs.
BTW, if you go to any retail establishment, including House of Fish, you will pay more. This is a great deal and someone should jump on it immediately.
I'm going out on a limb here, but I think Kasei is unloading this because of a new toy he just purchased (Ca reactor).