Centre of mass is the point at which the distribution of mass is equal in all directions, and does not depend on gravitational field. The distribution of mass is critical for the success of skill movements regardless of rotations or axis directions.
With this is mind, it is always recommended to enter the value for Center of Gravity when using Mirai. Failure to provide this data point can lead to unexpected behaviors such as "jittery" guidance movements, inverted directionals when guiding, and possible failed training episodes.
For more information and steps to configure the CoG click here: Tool Mass & Center of Gravity (CoG) Measurement Wizard