The Integer format measures the maximum range between real data points, and determines a scale factor. The data is then scaled to that range when saved to the c3d file, and all values are written with the Integer format. When the data is then read into another program (i.e. Polygon), the scale factor is applied to the data converting it into Real data. The real data format saves the data as is without any multiplication by a scale factor and writes it to the c3d file utilizing the Real format. Certain types of data are best suited for the Real format option since no resolution is given up in the storage of the data. Not all programs may be able to read both Integer and Real formatted c3d files, so use care when choosing your preferred option. More details on the .c3d format are available on C3D.org