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 5-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 children at Grace Field House have their numbers ending with 94. Isabella, Krone, Leslie, Matilda, and Cecile all have their numbers ending with 84. 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.

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 4 to 5 per year per farm plant, with one shipment approximately every 2 months. This would in turn mean that there are 5 shipments each 2 months from the entirety of Grace Field House, or 20 to 25 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 30 children are born each year and in turn fits with there being 6 children of the same age each plantation until the age they can be shipped out, such as the children who were between 3 and 5 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 3 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 5 years (2014 vs 2019) and their IDs are 150 digits apart. This suggests that Grace Field harvests 30 children annually; each house harvests 6 children from each plant annually, or one roughly every 2 months. This is consistent with the "adoption" of a child every two months. Extrapolating further, Grace Field would've been in operation for about 1,638 years when Emma was born.