Grace Field House Numbering

''This article is about the Manga version of the Grace Field House numbering. For alternate pages referred to by this name, please click any of the icons above.''

The Numbering on the neck is a standard identification procedure for all children that come to the Grace Field House orphanages. Like livestock, they are marked before they reach the farm. These marks are always on the left side of the neck and are always five-digit numbering. Mamas, Sisters, and Grandma like any other adult human in the Hierarchy of the Demons, also have an identifying number.

Understanding and Analysis
At first glance, the numbers appear to be random, except for the fact that they all have five digits. However, when read from right to left the ID Numbers have a clear order with the oldest adults having the lowest ID Numbers and the number getting higher the younger the children are.All of the children currently residing at Grace Field House have numbers ending with 94. Isabella, Krone, Leslie, Matilda, Sienna, and Cecile all have their numbers ending with 84. This is due to approximately 1,000 more children being born at Grace Field from the time the aforementioned characters were born to 2045 when the story begins, which caused the fourth digit (or second digit when reversed) to go up by one. The children are assigned false birthdays to prevent the Mamas and Sisters from knowing which baby is theirs, so the order of the ID Numbers may not accurately reflect their birth order. However, the closer two children are in age, the closer their ID Numbers will be to one another. So even if the ID Numbers do not accurately reflect birth order, it is likely very close to their real birth order, only being off by months or mere days.

The diagram below is organized according to the age of the characters in 2045.

Theories derived from the numbering
There is an estimate quoted in the manga that freight shipments range from five to six per year per plant, with one shipment approximately every two months. This would in turn mean that there are five shipments each two months from the entirety of Grace Field House, or 25 to 30 per year. The 20-year age gap between Isabella and her son Ray indicates that 581 children were born, and presumably shipped out, in this time, which would mean that around thirty children are born each year and in turn fits with there being six children of the same age each plantation until the age they can be shipped out, such as the children who were between three and five years old at the time of the escape in 2046.

Unique Identifiers
It is later revealed that this kind of 'marking' is unique to and used only inside the Grace Field House. The other three Premium Farms use other ways to mark the children. This differs greatly from the Factory Farms who use brands to mark their livestock.

Trivia

 * In a commentary on the 12th edition of Weekly Shonen Jump, Kaiu Shirai commented that there were people who already discovered the pattern of the reversed numbers and this surprised him.
 * It is possible that the ID numbers on the children's necks are allocated serially and are meant to be read from right to left
 * Leslie is the oldest known orphan from Grace Field and has the ID 71584 (48517). Isabella is the next oldest and has the ID 73584 (48537). Emma, Norman and Ray are the same age and have IDs 63194 (49136), 22194 (49122) and 81194 (49118) respectively. From this, it can be deduced that Ray is the eldest, followed by Norman and Emma.
 * Isabella and Krone have an age gap of five years (2014 vs 2019) and their IDs are 150 digits apart. This suggests that Grace Field harvests thirty children annually; each house harvests six children from each plant annually, or one roughly every two months. This is consistent with the "adoption" of a child every two months.
 * The Grace Field Identifiers are currently the only known farm identifiers to be made up of only numbers.
 * While Sarah's exact identification number is unknown, it most likely ends in "74". There are thirty children born at Grace Field each year and twenty one years between Sarah and Isabella's birth. Doing the math, that would place Sarah's identification number somewhere around 78874 (47887).
 * Doing the math further, The Previous Grandmother would most likely have an ID number somewhere around 00274 (47200).
 * Marcus, Susan and Helena have ID numbers that do not correspond with their ages.
 * Having the ID numbers read right to left makes it easier to see each individual's ID number as the most frequently changing numbers are in the front.