• 25.4 baseline — 0.6 × season 25.3 (12 gm) + 0.4 × last 10 25.4
• −1.8 opponent leak — they concede 343.2/game vs a 369 league average
• −6.7 at this ground — averages 18.7 there (50 gm)
• vs them: averages 21.6 over 5 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.