• 12.5 baseline — 0.6 × season 12.0 (4 gm) + 0.4 × last 10 13.3
• +0.2 opponent leak — they concede 375.7/game vs a 369 league average
• +2.8 at this ground — averages 15.3 there (10 gm)
• vs them: averages 19.0 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. Round 22: 2 — far outside his usual range; kept in the average, not smoothed away.