• 3.8 baseline — 0.6 × season 4.0 (19 gm) + 0.4 × last 10 3.4
• −0.1 opponent leak — they concede 92/game vs a 93.4 league average
• −0.3 at this ground — averages 3.4 there (48 gm)
• vs them: averages 2.6 over 8 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.