How is Until_date in t_ep_CTO_matrix derived ?

hello All, Can anybody suggest us how the until_date in t_ep_Cto_matrix gets derived. we know it depends on various factors but we see some discrepencies like there is an item / location combination we see it until date till 03-Dec-2016 but there are items which are also not having much history but they have it till 3-Mar - 2018 . Can somebody throw some light on the different behavior we see here . Let me know in case you require any more detail om this . Regards, Sakshi Thakur