• 6.2 baseline — 0.6 × season 6.0 (15 gm) + 0.4 × last 10 6.5
• −0.4 opponent leak — they concede 200.3/game vs a 213.6 league average
• −1.9 at this ground — averages 4.3 there (18 gm)
• vs them: averages 1.0 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.