BM: please read a little bit about natural selection.
If a mutation is not beneficial, it does not carry on to subsequent generations (I am oversimplifying a little). This involves a similar explanation to why proteins fold, although they should not, according to "your" math. A protein is a huge molecule, with many chemical bonds. These bonds can rotate, and this creates an enormous, astronomical combinatorial space of particular angles. So how come, a Creationist would ask, that an enzyme can fold into an organized structure? Yet we know that they fold, and the concept of cumulative selection (accepting PARTIALLY correct organization and thus pruning the tree of possibilities) provides the answer as to why.
Sorry, not buying it. And I done a lot more research than you’ll ever know.
Extinctions are often caused by deleterious mutations.
Although rare, fatal mutations can be copied into the offspring [obviously they are not immediately fatal].
Furthermore, for all mutations, the beneficial mutations number approx 1 in a million.