• 7.0 baseline — 0.6 × season 6.6 (17 gm) + 0.4 × last 10 7.5
• −0.5 opponent leak — they concede 30.4/game vs a 32.7 league average
• −2.0 at this ground — averages 5 there (45 gm)
• vs them: averages 5.5 over 2 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.