Thanks!
No, ITN goes from 10.300 (worst) to 1.000 (best), where you can only reach something below 1.500 through your ATP points, e.g. Thiem has 1.300, Ofner has 1.250. If you win against an opponent with a lower ITN, you reduce your ranking and vice versa.
And, by the way, Austria (Thiem) not...