• 2.6 baseline — 0.6 × season 2.6 (10 gm) + 0.4 × last 10 2.6
• +0.0 opponent leak — they concede 57.5/game vs a 56.6 league average
• +0.1 at this ground — averages 2.7 there (44 gm)
• vs them: averages 3.6 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.