• 52.0 baseline — 0.6 × season 50.9 (11 gm) + 0.4 × last 10 53.7
• +0.5 opponent leak — they concede 548.9/game vs a 544.2 league average
• −5.0 at this ground — averages 47 there (4 gm)
• vs them: averages 24.7 over 3 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.