# C491 — Close the cross-tradition source explanation

## Question

Can every unit of LXX’s cumulative890 difference be traced to supplied lifespan rows?

## Inputs

```json
{
  "Lamech": -24,
  "Arphaxad": 27,
  "Cainan": 460,
  "Shelah": 27,
  "Eber": 40,
  "Peleg": 100,
  "Reu": 100,
  "Serug": 100,
  "Nahor": 60
}
```

## Sources

```json
[
  "File18 §§2.2,4.1–4.2,6D; corrected339/339/330 triplet"
]
```

## Opened utc

2026-09-27T22:40:15.843136+00:00

## Results

```json
{
  "row_deltas": {
    "Lamech": -24,
    "Arphaxad": 27,
    "Cainan": 460,
    "Shelah": 27,
    "Eber": 40,
    "Peleg": 100,
    "Reu": 100,
    "Serug": 100,
    "Nahor": 60
  },
  "postFlood_without_Cainan": 454,
  "all_deltas": 890,
  "endpoint_check": 890
}
```

## Finding

The total is454+460−24=890. Alongside SP’s−608, this completes a source-row explanation of why the regular and cumulative families move differently. A common projection grammar is supported; a common12026 endpoint is not.

## Reassessment

Return to the MT rounded/actual interface and derive its residual conservation from rows and endpoint selections.

## Checks

```json
{
  "total": true,
  "postFlood": true,
  "regular_independent": true
}
```

## Closed utc

2026-09-27T22:40:15.843363+00:00

## Record provenance

Exact record hash: `09851060f453b478462087352850941d9c1e72097fcda695304666ec74bf6567`

Source journal: `Research_Cycles/C0482_C0531/journal.json`