• 5.1 baseline — 0.6 × season 5.5 (19 gm) + 0.4 × last 10 4.6
• +0.3 opponent leak — they concede 164.6/game vs a 155.4 league average
• −0.6 at this ground — averages 4.5 there (26 gm)
• vs them: averages 6.5 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.