In Psalm 139 – Does God use His Book (סִפְרְךָ) to document ‘our design’ or ‘our time’ on Earth?

In Psalm 139 – Does God use His Book (סִפְרְךָ) to document ‘our design’ or ‘our time’ on Earth?

Tehillim (Psalms) 139:16 [MT] : "Your eyes saw my unformed body, and on Your Book they were all written; days have been formed and one of them is His." (גָּלְמִ֚י | רָ֘א֚וּ עֵינֶ֗יךָ וְעַל־סִפְרְךָ֘ כֻּלָּ֪ם יִכָּ֫תֵ֥בוּ יָמִ֥ים יֻצָּ֑רוּ וְל֖וֹ (כתיב וְלֹ֖א) אֶחָ֣ד בָּהֶֽם)

Psalm 139:16 [KJV] : "Thine eyes did see my substance, yet being unperfect; and in thy Book (all my members) were written, which in continuance were fashioned, when as yet there was none of them."

Psalm 139:16 [NIV] : "Your eyes saw my unformed body; (all the days ordained for me) were written in Your Book before one of them came to be."