• 6.3 baseline — 0.6 × season 6.4 (19 gm) + 0.4 × last 10 6.3
• +0.5 opponent leak — they concede 100.5/game vs a 93.4 league average
• −0.5 at this ground — averages 5.8 there (62 gm)
• vs them: averages 5.2 over 5 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.