• 5.7 baseline — 0.6 × season 5.7 (7 gm) + 0.4 × last 10 5.8
• +0.3 opponent leak — they concede 224.7/game vs a 213.6 league average
• −0.5 at this ground — averages 5.3 there (4 gm)
• vs them: averages 4.0 over 1 game — 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.