• 5.0 baseline — 0.6 × season 4.8 (19 gm) + 0.4 × last 10 5.4
• −0.0 opponent leak — they concede 93.2/game vs a 93.4 league average
• +0.6 at this ground — averages 5.7 there (12 gm)
• vs them: averages 5.9 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.