SparkFun BasicAHRS_I2C giving unstable readings
If you haven’t noticed the difference in the two is minuscule. 
For example, the change in degree is &lt;1. Also the acceleration is measured in g’s which is acceleration due to gravity. The data says the measures are in mg which is 0.01g. 
This is normal with accelerometers and all sensors when they pick up residual voltage from random vibrations or other sources of noise. It also could be with the error margin within SparkFun’s product since the product is more on the lower end of quality which once again is normal. 
TLDR: everything is working fine.