There are samples and samples that seems to get mistaken with each other.. Not just you, i think even James had something else in mind at beginning of this journey ;) (technical specs has a line, which says you can log over a week to a 32GB card at max rate, when real life logging gives us few MB:s of data when doing stupidly fast logging ;))
From mooshimeter app main screen, you get to settings by pressing gear symbol on upper right corner. There you can set “Logging Interval”, which is the rate of results saved to memorycard. “No wait” saves few times per second and rest should be self explanatory (1s, 10s, 1min, 10min).
At app main screen again, on the bottom, there are other sample rates to play with, but those just tell the meter how to deal with actual measuring and calculations. I have my meter now in “current ac” and “voltage ac” modes, both rates on “auto” and those say 4000Hz and 256smpl. If i understand this right, mooshimeter is now doing its thing 256 times, in rate of 4000Hz, then calculating values to show on a screen (and to log, if that is on) and then getting next 256 values again and again. So it has “nothing to do” with save rate, only how to get that actual data to a form that it makes sense. If only one sample is taken from mains voltage (lets say 230v/50Hz in most of europe), it would be any value between about -300 and +300 volts. That would be totally unusable. You can tap to that data in graph mode and setting buffer mode on, where you can see few hundred of actual datapoints at a time, but as far as i know, we cant log that way (yet?).
There might be some real life situations where saving couple buffers at a time at slower log rate would came in handy, just not sure what it would be :D Maybe to check quality of electricity.. Short spikes would escape our loose net, but it might tell something.
Sorry for such a long answer, what was the question? :D