The Movies animation files (*.anm) contain bone animations and prop animations. Bone animations use an armature and the location and orientation of each bone is specified for each frame in the animation. Since most armatures have lots of bones and animations can have hundreds of frames, that amounts to a lot of data. In order to save space in the files, the key frame data is compressed to fit into a 16 bit signed integer.
int16 = float/compression
where "compression" is the largest absolute value in the data.
For rotation data, the range of angles is restricted to -180 to 180. The compression factor is 180, so all stored values are between -1 and 1. Since any angle can be reduced to the range -180 to + 180, the compression value for angles never changes.
For location data, however, the situation is more complex. It is desirable to use as small a compression value as possible because that gives more precision in specifying location,