• 27.2 baseline — 0.6 × season 25.8 (20 gm) + 0.4 × last 10 29.3
• +1.5 opponent leak — they concede 389.2/game vs a 369 league average
• −2.7 at this ground — averages 24.5 there (16 gm)
• vs them: averages 18.8 over 13 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.