It's a landmark for a young child to count to 100; it sort of covers all the "ordinary" numbers. One hundred is obviously significant for other groupings: 100 cents is a dollar; 100 yards is a touchdown; 100 years is a century, and the landmark for a very long life. It makes sense, then, that in the Bible, 100 represents fullness or a state of completion, or in some instances simply "much." For instance, people marvel that Abraham had Isaac when he was 100 years old; the number represents the point at which the Lord, when growing up as Jesus, united the human elements of himself with the divine elements and in a sense became "complete.

927. 'I will curse the ground no more on account of man' means that never again would man thus turn himself away as the people who belonged to the descendants of the Most Ancient Church had done. This is clear from what has been stated already about the descendants of the Most Ancient Church. 'Cursing' in the internal sense means turning oneself away; see what has appeared already in 223, 245.

[2] The implications of these matters and of those that follow, namely that never again would man thus turn himself away as the member of the Most Ancient Church had done and that he would never again be able to destroy himself in that way, also becomes clear from what has been stated already about the descendants of the Most Ancient Church who died out and about the new Church called Noah. That is to say, the member of the Most Ancient Church was one in whom will and understanding formed one single mind, that is, with him love was implanted in the will part of his mind, and so at the same time faith, which occupied the second or understanding part. Their descendants therefore inherited a will and an understanding that made one. Consequently when self-love and resulting insane desires began to take possession of their will part where love to the Lord and charity towards the neighbour had been previously, not only did the will part, or the will itself, at that point become utterly corrupted, but so also at the same time did the understanding part, or the understanding itself, all the more so when the final descendants immersed falsities in their desires and in so doing became the Nephilim. They became the kind of people therefore for whom no restoration was possible since both parts of their mind, that is, their whole mind, had been ruined.

[3] Foreseeing this however, the Lord also made provision for mankind to be rehabilitated in the following particular manner: Man could be reformed and regenerated as regards the second part of his mind, the understanding part, and a new will, which is conscience, could be implanted in him, by means of which the Lord might stimulate the good that stems from love or charity, and the truth of faith. In this way did the Lord's Divine mercy restore man. These are the things meant in this verse by 'I will curse the ground no more on account of man, for the imagination of man's heart is evil from his childhood', and by 'I will no more strike every living thing, as I have done'.