Ok, leaving as 1000.

Wikipedia for (megabyte) says: The megabyte (abbreviated as Mbyte or MB) is a multiple of the unit byte for digital information storage or transmission with three different values depending on context: 1048576 bytes (220) generally for computer memory;[1][2] and one million bytes (106, see prefix mega-) generally for computer storage.[1][3] In rare cases, it is used to mean 1000×1024 (1024000) bytes.[3] The IEEE Standards Board has confirmed that mega- means 1000000, with exceptions allowed for the base-two meaning.[3]