Why was Hannibal killing in sounders?

I have been re-watching the TV series Hannibal and while discussing the MO of the Chesapeake Ripper (Hannibal Lecter), it was revealed that he had been previously killing his victims in groups of 3, also refereed to as "sounders"

As the Chesapeake Ripper, Lecter kills in sounders (referring to a small group of pigs) of three. That is how he sees his victims, not as people, not as prey, but as pigs. Though crime scene photos show that his exact method varies, his victims are killed and mutilated by cutting, sometimes dismembered, and what remains of them is left on display and posed in various theatrical ways; one of the most frequently mentioned ways was when the Ripper left a victim near a church pew and used his severed tongue as a page marker in a bible he was reading. He also removed and took with him certain organs from the victims, which he, unbeknownst to the FBI, consumed.

As a fan of the source material, I do recognize how brilliant it was to go about depicting his MO in this way, since Hannibal does surely see most of his victims as pigs, but also because pigs are very thematic to Hannibal self-titled novel and film.

However, I was wondering, where did Hannibal get this specific idea to do so from? Is there any reason that it is a group of 3?

Maybe I'm wrong, but I don't remember either the Red Dragon novel or the TV-show ever explaining or confirming this was Hannibal's intent/reasons for going about it like this. Is this about practicality perhaps? Would the organs from 3 bodies be enough to sustain Hannibal's means for 11-18 months? (Probably not given he was also picking rude people to eat from his Rolodex.) Maybe Bryan Fuller or one of the other EPs can shed some light on this?