CREATE TABLE table_1718 ("COMPANY NAME" TEXT, "Holding Companies" FLOAT, "Subsidiaries" FLOAT, "Description of activities" TEXT, "Parent  ( holding )  company" TEXT)

How many subsidiaries are there of Postermobile Advertising Limited?
SELECT MIN("Subsidiaries") FROM table_1718 WHERE "COMPANY NAME" = 'POSTERMOBILE ADVERTISING LIMITED'
SELECT MIN("Subsidiaries") FROM "table_1718" WHERE "COMPANY NAME" = 'POSTERMOBILE ADVERTISING LIMITED'