• 3.7 baseline — 0.6 × season 3.9 (7 gm) + 0.4 × last 10 3.4
• −0.5 opponent leak — they concede 49/game vs a 56.6 league average
• −0.6 at this ground — averages 3.1 there (10 gm)
• vs them: averages 2.0 over 1 game — 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.