• 2.6 baseline — 0.6 × season 2.5 (13 gm) + 0.4 × last 10 2.8
• +0.7 opponent leak — they concede 117.8/game vs a 93.4 league average
• +2.3 at this ground — averages 4.9 there (18 gm)
• vs them: averages 6.6 over 12 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.