This specifies the maximum allowable difference in value between the start frame and the other frames. If the difference remains less than this specified tolerance, the animation is assumed to be fixed and is exported using only the value for the start frame.

When animation curve data is created automatically from baked data, a key is created for each frame (in the units specified by Frame Precision. Keys are deleted if the maximum error value when performing Hermite interpolation is less than the tolerance value specified here. The smaller the error tolerance, the greater the animation precision. However, as the number of keys grows larger, the amount of animation curve data also increases.