user: ### NOW ANSWER:
Question: WHat matcH number Has a ground of H and tHe opponent Chelsea Under 18s?
Columns: ['Match', 'Date', 'Competition or tour', 'Ground', 'Opponent', 'Score1']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '23 August 2008', 'Premier Academy League', 'H', 'Manchester United Under 18s', '0 - 0']
SQL:

assistant: SELECT AVG("Match") FROM "Table" WHERE "Ground" = 'H' AND "Opponent" = 'Chelsea Under 18s';