• 2.0 baseline — 0.6 × season 2.1 (14 gm) + 0.4 × last 10 1.9
• −0.1 opponent leak — they concede 31.7/game vs a 32.7 league average
• +1.3 at this ground — averages 3.3 there (22 gm)
• vs them: averages 2.5 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.