OFFSET           Offset into group/segment                           Operator

  OFFSET expression

    Returns the offset of expression within the current segment (or the
    group that the segment belongs to), if using simplified segmentation
    (MODEL) or Ideal mode.

    In MASM mode, when using generic segmentation (SEGMENT), any data
    item in a segment that is part of a group is considered to be
    principally a member of the segment, not of the group. An explicit
    group override must be used for Turbo Assembler to recognize the data
    item as a member of the group.