Attempting to save hourly data over a 24-hour period with a GMC-300 with firmware version "GMC-300Re 2.33" fails to save any count data.
Here's some raw data extracted from the 64 KiB memory via the USB serial interface:
07A0: 0D 03 04 10 13 39 55 AA 03 55 AA 00 0D 03 04 10
07B0: 15 1D 55 AA 03 FF FF FF FF FF FF FF FF FF FF FF
This data shows a start time of 2013-03-04 16:21:29 and a count interval of one hour (55 AA 03), but no count data is ever recorded into the unused space (FF) even after the GMC-300 has run for 24 hours with the save data symbol clearly shown on the display.
An earlier test to save data "Every Minute" on the same device worked as expected.