The surprising thing here is that God beforehand (in the womb already!) knew all the days of my life. He wrote them down, so to speak, in his book. No man can do a thing like this.
We can only jot down the facts of a certain day, after it has happened. Again, we are in awe of an almighty and all-knowing God.
16 Your eyes saw my unformed substance; in your book were written, every one of them, the days that were formed for me, when as yet there was none of them.