• 10.3 baseline — 0.6 × season 10.3 (19 gm) + 0.4 × last 10 10.4
• −0.2 opponent leak — they concede 152.3/game vs a 155.4 league average
• −2.8 at this ground — averages 7.6 there (32 gm)
• vs them: averages 7.5 over 2 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.