Gumb's suit of skin (shown hanging on a mannequin in his basement, late in the movie), needs skin patches for the left thigh and upper-left chest area, before it will be complete. He plans to get the chest area from Catherine Martin. (Later in the movie, when Clarice Starling shows up at his door, he looks Starling over and comes to believe that he can kill her and then get the left thigh piece from her).
Looking again at Lecter's Memphis prisoner number, 'B5160-8', it has already been observed that '516' is a reference to Deuteronomy in the bible, specifically, that part which talks about the Passover. The zero doesn't really mean anything, it is just there to make the numerical clue not too obvious. To find out what the meaning of the '8' in the prisoner number is, Saint Augustine's Confessions, Book 13 chapter 29, in which Augustine speaks to God about the creation of the world, needs to be looked at again: "And I looked attentively to find whether it was seven or eight times that you saw your works were good, when they were pleasing to you, but I found that there was no 'time' in your seeing which would help me to understand in what sense you had looked so many times at what you had made..."
The mention of the number seven in the above passage, has to do with the fact that if Gumb kills Catherine Martin, and adds a piece of her skin to his 'suit', he will have completed seven days of 'creation' (recall that Martin is Gumb's intended seventh victim). Lecter (personification of Satan/evil hermaphroditic Jews) and Gumb (Satan's pupil/evil Freemasons) together had earlier worked out a plan, whereby the suit would need just seven pieces to be complete. Gumb's act of making the suit is being 'overseen' by Lecter (implying that Lecter and Gumb have met at least once, having been placed in contact with each other by Benjamin Raspail, one of Lecter's past patients). However, if one watches the 'chase' scene in the basement carefully, he or she will notice the view of the skin suit hanging on a mannequin in Gumb's basement, in such a stage of completion which shows that Gumb will need not just Martin's skin, but one more victim, that is, eight total to complete the suit (as shown in the above screencap). This is a reference to the mention of the number eight by Augustine in the above passage, and it is the reason for the '8' in Lecter's Memphis prisoner number. Lecter comes to discover that Gumb needs an eighth piece (as will be explained later), and part of what Hannibal is doing by sending Clarice to Gumb via the clues he has been giving her, is setting things up so that Gumb will think he can get the eighth piece from Starling.
Starling is an 'agent' of God, sent to Earth to destroy Gumb. Lecter, representing absolute evil, recognizes Starling as this holy agent (i.e., as an angel of death). But, she does not know that Lecter can tell this because, she does not know herself that she is this angel. When God sent Starling, he had to keep her ignorant of her true identity; otherwise, she would not 'mix' well with humanity. God has sent her such that she operates under the pretext of being a person who catches criminals (as implied, with her not knowing that this is only a pretext). This will provide her 'human reason' to kill Gumb. But as stated, Lecter has recognized Clarice as this agent from God, so he knows she must be destroyed, thereby preserving Gumb's life.
But, Lecter also has an ace up his sleeve, which will provide him with an 'out' should his plan to have Starling killed fails: Recall that the goal of Clarice's psychoanalysis, under Dr. Lecter, is for her to become a grown, sophisticated woman - a real woman; this is to be taken as real in the truest sense. If Starling defeats Gumb, who represents the inauthentic woman within her, she will have been completely 'converted' into an ordinary human being, and she will no longer be an angel of death. In analyzing Starling, Lecter is to get her to believe that she must confront Gumb to become a complete woman. However, Lecter ultimately desires that she lose this confrontation.
No matter how the confrontation turns out, however, Lecter 'wins': He sends Starling to Gumb with the hope that Gumb will kill her, as already stated; but if things turn out the other way around, Starling will no longer be a holy agent (due to the above-mentioned conversion of her into a real, i.e. fully human, woman), so Lecter, as evil personified, will be free (once he escapes from prison in Memphis) to roam and wreak havoc, and continue his work, without being impeded by her.
The Confessions of Saint Augustine (Outler)
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