• 5.7 baseline — 0.6 × season 5.9 (18 gm) + 0.4 × last 10 5.4
• −0.3 opponent leak — they concede 203.2/game vs a 213.6 league average
• +0.0 at this ground — averages 5.8 there (33 gm)
• vs them: averages 6.3 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.