Library /sys$common/syshlp/dbg$help.hlb DEBUG, Language Support, BASIC, Line Numbers  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The sequential line numbers that you refer to in a debugging
    session and that are displayed in a source code display are
    those generated by the compiler. When a BASIC program includes
    or appends code from another file, the included lines of code are
    also numbered in sequence by the compiler.