One question runs through every attempt to relate the yuga figures to history: are the years human years or years of the gods? The Manusmriti and the Puranas describe a divine year as 360 human years, and the yuga totals are given in the sources both as figures of divine years and as the very much larger figures obtained by multiplying by 360. The 1,296,000 years of the Treta is the multiplied figure; the underlying count is 3,600 divine years.
This is not a modern confusion. The sources themselves work with both scales, and the commentators discuss the relation, so a reader meeting two sets of numbers for the same age is meeting a real feature of the tradition rather than an error in transmission.
It is also the opening through which every modern reinterpretation has come. If the base figures are divine years, then the choice of multiplier is where a reformer can intervene, and reformers have. The atlas records the traditional multiplied figures as the tradition gives them, notes that the smaller figures are equally traditional, and treats the question of which is meant as one the sources leave open rather than one a reference work should settle by preference.
The Treta is also where the yuga scheme meets narrative. The Ramayana is placed in this age, and the epics and Puranas locate their events within the cycle rather than in any absolute chronology, which is one of the ways the scheme functions in practice: it is a frame for ordering the tradition's own material as much as a cosmological measure. That is a different use from dating, and the two should not be confused.