• 5.5 baseline — 0.6 × season 5.3 (16 gm) + 0.4 × last 10 5.8
• +0.0 opponent leak — they concede 94/game vs a 93.4 league average
• −0.5 at this ground — averages 5 there (6 gm)
• vs them: averages 6.1 over 8 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.