大方廣圓覺修多羅了義經略疏 2.1273

2.1273

此有二意：一者，先用數息觀門治諸覺觀，漸入妙境。然修出入息者，有六妙門：謂一數、二隨、三止、四觀、五還、六淨，或依次第、或隨便宜，廣如疏釋；二者，即下所知生滅心念，便是數門。

This has two meanings: first, initially using the contemplation approach of counting breaths to cure initial and sustained thought, gradually entering the marvelous realm. However, in cultivating inhalation and exhalation, there are six marvelous gates: namely, first, counting; second, following; third, stopping; fourth, contemplating; fifth, returning; and sixth, purifying. They may be followed in sequence or taken according to convenience, as detailed in the commentary. Second, the thoughts of arising and ceasing known below are themselves the approach of counting.