• 49.2 baseline — 0.6 × season 47.1 (17 gm) + 0.4 × last 10 52.3
• +4.4 opponent leak — they concede 594.4/game vs a 545.7 league average
• −22.2 at this ground — averages 27 there (4 gm)
• vs them: averages 31.8 over 4 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.