• 10.0 baseline — 0.6 × season 9.8 (4 gm) + 0.4 × last 10 10.4
• −0.1 opponent leak — they concede 365.8/game vs a 369 league average
• +3.6 at this ground — averages 13.6 there (7 gm)
• vs them: averages 15.0 over 1 game — 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.