• 21.4 baseline — 0.6 × season 24.3 (16 gm) + 0.4 × last 10 17.2
• +0.1 opponent leak — they concede 546.2/game vs a 544.2 league average
• +7.1 at this ground — averages 28.5 there (6 gm)
• vs them: averages 13.2 over 5 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.