• 6.4 baseline — 0.6 × season 6.3 (18 gm) + 0.4 × last 10 6.5
• −0.1 opponent leak — they concede 152.3/game vs a 155.4 league average
• −1.7 at this ground — averages 4.6 there (14 gm)
• vs them: averages 6.0 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.