user: Question: What's the highest Pl GP with a Reg GP over 18?
Columns: ['Rd #', 'Pick #', 'Player', 'Team (League)', 'Reg GP', 'Pl GP']
Types: ['real', 'real', 'text', 'text', 'real', 'real']
Sample row: [1.0, 23.0, 'Ryan Kesler', 'Ohio State University ( NCAA )', 578.0, 57.0]
SQL:

assistant: SELECT MAX("Pl GP") FROM "Table" WHERE "Reg GP" > 18.0;