/sys$common/syshlp/helplib.hlb MACRO, VAX MACRO Assembler, Operand Formats, Branch  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The address is stored as an implied displacement from the  PC.
    This mode  can  be used only in branch instructions.  The
    displacement for conditional branch instructions and the BRB
    instruction is stored  in a byte.  The displacement for the BRW
    instruction is stored in a word (two bytes).  A byte displacement
    allows a range of 127 bytes forward and  128 bytes backward.  A
    word displacement allows a range of 32767 bytes forward and 32768
    bytes backward.  The displacement is relative to  the  updated  PC,
    the  byte  past  the  byte  or  word where the displacement is
    stored.

    address

    address

    An expression that represents an address.