The Numbering in the neck is a standard identification procedure in all children who come to orphanages. Like animals, they are marked before they reach the farm. These marks are on the left side of the neck and is a 5-digit numbering. Mamas and Sisters, like any other adult human in the Hierarchy of the Demons, has a numbering.
Understanding and Analysis
At first glance, the numbers appear to be random except for the fact that they all have five digits. But by reading the numbers back and forth, you can see that they have a clear order.
See the diagram below, which is organized according to the age of the characters.
Theories derived from the numbering
There is an estimate quoted in the manga that freight shipments range from 4 to 5 per year per farm. The 15-year interval between Isabella's and her son, Ray's numbering indicates that 500 children were transported. If the date of the "invasion" of the demons was correct, about 30 years ago, then the numbering of the children began around the number 48000.
It is later revealed that this kind of 'marking' is unique and only used inside the Grace Field House. The other 3 Premium Farms use other ways to mark the children. This differs greatly from the Factory Farms who use brands to mark their livestock.
- In a commentary on the 12th edition of Weekly Shonen Jump, Kaiu Shirai commented that there were people who already discovered the rule and this surprised him.