• 1.5 baseline — 0.6 × season 1.6 (18 gm) + 0.4 × last 10 1.4
• −0.1 opponent leak — they concede 33.9/game vs a 35.7 league average
• +0.7 at this ground — averages 2.3 there (97 gm)
• vs them: averages 2.1 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.