USCIS announcement on 10/3/2017:
H-1B visas provide skilled workers for a wide range of specialty occupations, including information technology, engineering, and mathematics. When a petitioner requests the agency’s premium processing service, USCIS guarantees a 15-calendar day processing time. If that time is not met, the agency will refund the petitioner’s premium processing service fee and continue with expedited processing of the application….
Details about premium processing are found at the USCIS website.