• 6.1 baseline — 0.6 × season 5.9 (19 gm) + 0.4 × last 10 6.4
• −0.3 opponent leak — they concede 34.2/game vs a 35.7 league average
• −3.5 at this ground — averages 2.6 there (67 gm)
• vs them: averages 4.1 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.