Which one do you have? settings on the board will guide how fast you should read from those (I’ve seen 50Hz)
Reading quickly from different analog pins can be erratic. you might want to read twice in a raw and only keep the second read
The Ardulog runs at 3.3V so most probably it’s analogref is at 3.3V whereas on your uno it will be at 5V hence the difference in the readings
You’ll get a range of reading from 0v for -3G to +3.3v for +3G.