Sept 17 (Reuters) - Iran has revised the official selling price (OSP) of its Soroush and Norouz grades for October delivery to Asian buyers to $7.23 a barrel below the price of Iranian Heavy, the National Iranian Oil Company said on Tuesday.     The prices were revised from those posted on its website on Monday.     The company on Monday set the October Iranian Heavy OSP at $1.08 a barrel above the Oman/Dubai average. Official selling prices for Iranian Light and Forozan grades were unchanged.      The table below shows August crude prices to Asia, as differentials to the Oman/Dubai average.     Prices for Soroush and Norouz are quoted as differentials to Iranian Heavy. All prices are in U.S. dollars.           Grade                 Oct            Sep      IRANIAN LIGHT         +3.61          +3.08      IRANIAN HEAVY         +1.08          +0.74      FOROZAN               +1.35          +0.96      SOROUSH            IH -7.23       IH -6.89      NOROUZ             IH -7.23       IH -6.89    (Reporting By Jacob Gronholt-Pedersen; Editing by Dale Hudson)  ((jacob.pedersen@thomsonreuters.com))  Keywords: IRAN OSP/