金剛經纂要刊定記 1.20

1.20

并序者，并謂共兼及也。序者敘也，敘述經疏之意故。又序者緒也，謂頭緒也。意明此半紙之言，是述疏入作之頭緒也。

"With Preface": "with" means together, combined, or reaching to. "Preface" (xu) means to narrate (xu), because it narrates the intention of the sūtra commentary. Also, "preface" (xu) means clue or thread (xu), indicating a beginning thread. The intention is to clarify that the words of this half-sheet of paper are the starting thread for composing this commentary.