user: Question: What is the total number of total viewers with a share of 18.8% and a weekly ranking under 16?
Columns: ['Episode No.', 'Airdate', 'Total Viewers', 'Share', 'BBC One Weekly Ranking']
Types: ['real', 'text', 'real', 'text', 'real']
Sample row: [1.0, '2 September 2011', 6114000.0, '24.2%', 9.0]
SQL:

assistant: SELECT SUM("Total Viewers") FROM "Table" WHERE "Share" = '18.8%' AND "BBC One Weekly Ranking" < 16.0;