substance... unperfect. unfinished substance. Not the same word as in Psalms 139:15. One word in Hebrew.
unperfect. Not imperfect.
Which in continuance. the days which were ordered, or in which they should be fashioned.
Related Commentaries of Psalms 139:16
Psalms 139:16
16 Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written,d which in continuance were fashioned, when as yet there was none of them.