from 19.5 baseline, −2.2 at this ground

• 19.5 baseline — 0.6 × season 19.4 (19 gm) + 0.4 × last 10 19.6
• −0.1 opponent leak — they concede 185.3/game vs a 186.1 league average
• −2.2 at this ground — averages 17 there against the player's own 19.2 in those same seasons — 89% of that level (18 gm)
• vs them: averages 12.0 over 1 game — 113% of the player's own level in those seasons — evidence, never summed

Derived, not measured — plain arithmetic over 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: 9 — far outside the usual range; kept in the average, not smoothed away.