Lynda,
In this specific instance, we are saying that "41 minutes 56.23 seconds" is one value and so must be dealt with as a whole. So, because "56.23" must be in Nemeth, the rest of this value must also be in Nemeth.
In other words, "72 minutes" would not need to be in Nemeth. Similarly, "72 minutes 12 seconds" would not have to be in Nemeth.
On the other hand, "43.5 minutes" would have to be in Nemeth. And "43.5 minutes 12 seconds" would have to be altogether in Nemeth.
Does that help to make the situation more clear?
–Kyle