Smoothing in SPM makes my files smaller

Hi,

I preprocessed my data with smoothing 10; I now want to change the smoothing level to 6 and I used the "Smooth" function in SPM12 for this. As "to be smoothed files" I used the wra files from my preprocessing. The initial files ("to be smoothed") are 71 173 KB. After smoothing, the swra files are just 666 KB. This gives problems with my further statistics.

If I do the preprocessing all over again, he smoothed files are the same size as the wra files.

Why is this happening and how can I help this?

Thanks in advance!