• 5.7 baseline — 0.6 × season 5.7 (17 gm) + 0.4 × last 10 5.6
• −0.3 opponent leak — they concede 88/game vs a 93.4 league average
• −3.2 at this ground — averages 2.5 there (4 gm)
• vs them: averages 4.5 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.