• 133.4 baseline — 0.6 × season 135.5 (15 gm) + 0.4 × last 10 130.2
• +2.8 opponent leak — they concede 1722.7/game vs a 1687.8 league average
• −1.5 at this ground — averages 131.9 there (38 gm)
• −17.9 wet forecast — averages 115.5 in the wet (13 gm)
• vs them: averages 134.6 over 7 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.