• 28.0 baseline — 0.6 × season 28.0 (10 gm) + 0.4 × last 10 28.0
• −0.9 opponent leak — they concede 333/game vs a 344.7 league average
• +5.7 at this ground — averages 33.7 there (18 gm)
• vs them: averages 45.0 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.