In Summation never had any pretenses of being anything but a sprinter, but stamina lurks in his background in the form of his second dam Fiesta Gal, a daughter of the great Alleged who won the 1987 Coaching Club American Oaks (USA-I). Sprinting stallions with some stamina in their backgrounds can often sire runners that stay better than they themselves did when given mares with some bottom to them.
In Calculator's case, this is a definite possibility. His dam Back to Basics is by Breeders' Cup Classic (USA-I) winner Alphabet Soup and is a half sister to Distorted Reality (by Distorted Humor), a stakes winner at nine furlongs. Calculator's second dam Christy Love is by Unbridled, another horse who had no trouble with 10 furlongs. Thus, it seems reasonable to conclude that Calculator at least has the potential of being able to stay 10 furlongs. Whether he will actually do so is another story, of course.
Further back, this is a very nice female line tracing back to the excellent broodmare Tamerett, whose five stakes winners include the versatile Tentam (by Intentionally), winner of the Metropolitan Handicap on the dirt and the United Nations Handicap on grass, and the 1980 Two Thousand Guineas (ENG-I) winner Known Fact (by Intentionally's best son, In Reality). In Reality is the male-line ancestor of In Summation, so Calculator represents the same cross of sire line over dam line. Tamerett also produced Secrettame (by Secretariat), dam of the fine racehorse and sire Gone West (by Mr. Prospector).
Generally speaking, the record of this family is one of miler speed which can be shorted by crosses to sprinting sires or stretched out by crosses to stayers. It's too soon to say if Calculator has inherited the right balance of stamina and speed to be able to carry top-level ability over Classic distances, but his performance in the Sham suggests that another furlong won't give him any trouble. Two more furlongs? We'll have to wait until May to get the answer to that one, but the answer could be "yes."