• 130.6 baseline — 0.6 × season 130.9 (14 gm) + 0.4 × last 10 130.2
• +2.3 opponent leak — they concede 1715.7/game vs a 1686.6 league average
• −5.0 at this ground — averages 125.6 there (55 gm)
• −18.1 wet forecast — averages 112.6 in the wet (12 gm)
• vs them: averages 133.8 over 10 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission.