This sample rate is for the samples -stored- in the log not the samples used for the decompression calculations so it doesn't really matter. When you download the log from the computer, it makes a difference in the "smoothness" of the curve showing the depth changes vs. time. It has nothing to do with what it displays during the dive for NDL's etc. The number of dives stores varies significantly according to the sample rate, it can be huge difference in how much it can store between 30 vs. 10s in sampling rate for the log. I don't know much exactly but it is probably proportional to the change in sampling rate.