• 108.9 baseline — 0.6 × season 106.8 (13 gm) + 0.4 × last 10 111.9
• +6.3 opponent leak — they concede 1785.8/game vs a 1687.8 league average
• +21.3 at this ground — averages 130.1 there (55 gm)
• vs them: averages 123.4 over 7 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.