• 26.7 baseline — 0.6 × season 26.3 (20 gm) + 0.4 × last 10 27.3
• +0.6 opponent leak — they concede 377.9/game vs a 369 league average
• −0.8 at this ground — averages 25.9 there (51 gm)
• vs them: averages 25.7 over 10 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.