• 25.9 baseline — 0.6 × season 25.8 (16 gm) + 0.4 × last 10 26.2
• +1.8 opponent leak — they concede 368.1/game vs a 344.7 league average
• −5.8 at this ground — averages 20.2 there (54 gm)
• vs them: averages 20.6 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.