• 2.3 baseline — 0.6 × season 2.3 (18 gm) + 0.4 × last 10 2.3
• +0.7 opponent leak — they concede 15.8/game vs a 12.2 league average
• −0.6 at this ground — averages 1.8 there (8 gm)
• vs them: averages 1.7 over 7 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.