Your calculations are approximate, but your process is on point, and I agree that 5.7e-5 is in the right ballpark.
However, given the prospective employer's insistence on pedigreed domestic hires, I doubt a significant portion of the applicant pool has ever spent time at any of the forbidden companies, as the companies listed are generally speaking Indian like Tata, Cognizant, Mahindra and Infosys; tend to hire a lot of Indians like Capgemini; or considered unattractive legacy enterprises in hopeless decline with Intel being the most prominent example.
In all likelihood,
the hiring manager and/or senior management at this startup probably just hate working with Indians, but can't overtly communicate "Indians need not apply" due to legal and PR considerations.
Actually kind of curious who the prospective employer is if
@Randomuser knows and is able to disclose.