The man who collects people with the eight different blood types for the Xindi to use in the creation of their biological weapon tells Archer and T'Pol that he has delivered people with six of the eight blood groups, and needs only provide an individual with "B-" and "AB+" for the complete set. When the Xindi attempt to deploy the weapon, Archer says to T'Pol that it is pointless for them to do so, as they only have six of the eight blood types. T'Pol replies that, still, they would destroy "75% of the human population." While 6 of 8 is, indeed, 75%, T'Pol is nonetheless mistaken based on the distribution of blood types among the human population. Only 3% of the human population have AB+ blood type, and only 2% of the population have B- blood type. As such, had Archer and T'Pol failed to thwart the Xindi from deploying the weapon, they would have, in fact, eradicated 95% of the human population, not 75% of the population, as T'Pol states.
When T'Pol and Captain Archer are transported 150 years into the past on earth you can see a skyline in the distance. This is not the Detroit skyline it is the Los Angeles skyline. The US Bank Library tower is easy to recognize even when blurred.