• 26.0 baseline — 0.6 × season 26.4 (20 gm) + 0.4 × last 10 25.4
• −1.7 opponent leak — they concede 345.4/game vs a 369 league average
• +0.5 at this ground — averages 26.5 there (83 gm)
• vs them: averages 24.4 over 9 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.