When Clay Kaczmarek merged with Desmond Miles, the latter learned of the former's knowledge of the calculations, which he later documented in a cell phone message memo. In the message, he noted several versions of himself: one who got married early and had a son, the reality who stayed single in New York, one who went to San Francisco to be a waiter, one who got a job at an auto body shop in Chicago, and one who never left The Farm in the first place.
Minerva later showed Desmond that if he did not use the Eye and release Juno from the Grand Temple, then the cataclysm would have destroyed humanity, but that he would lead the survivors in a restart of civilization. Long after his death, history would have repeated itself; Desmond would be worshipped as a god, but his teachings would be twisted to justify mass genocide.
Darby McDevitt has stated that "Calculations" is the in-house term for parallel universes in the series, and added that Clay Kaczmarek went insane because he saw too many possible futures, in addition to the Bleeding Effect.