While Aleph maybe the first letter, it is the number zero, not one. Some consider that this is the last letter after tav. Either way, it represents the place between the last and the first. The tarot card that represents Aleph is the Fool. The 2nd card the Magician (bet) is number 1.
Tsadde while being the 18th card, actually represents the number 17. Associated with the astrological sigh of Aquarius.