There's another reference Kauffman, (one of the authors), has made, where he calculates that the number of all possible combinations of proteins, having an arbitrary typical length of say, 200 amino acids, is so large, that given the known age of the universe, the universe cannot possibly have made all these protein combinations just once! (A typical protein is about 300 amino acids in length).
This then leads to the extraordinary conclusion that the universe has only explored a tiny, tiny subset of the possible proteins, of length 200 amino acids!
(I haven't yet looked closely at his math/assumptions in that calculation yet .. but the point he's making with it, underwrites a major part of his life's work in molecular evolution).