• 5.8 baseline — 0.6 × season 5.7 (21 gm) + 0.4 × last 10 6.0
• −0.2 opponent leak — they concede 31.4/game vs a 32.7 league average
• −1.4 at this ground — averages 4.4 there (19 gm)
• vs them: averages 3.0 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.