• 5.3 baseline — 0.6 × season 5.3 (13 gm) + 0.4 × last 10 5.3
• −0.3 opponent leak — they concede 88/game vs a 93.4 league average
• −0.2 at this ground — averages 5.1 there (70 gm)
• vs them: averages 4.1 over 9 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.