First, I config lessfs with the command:
# ./mklessfs ./examples/slave.cfg (the dta and mta are in the directory /data_lessfs/slave/dta, /data_lessfs/slave/mta)
# ./lessfs ./examples/slave.cfg /backup_lessfs/

# ./mklessfs ./examples/master.cfg (the dta and mta are in the directory /data_lessfs/master/dta, /data_lessfs/master/mta)
# ./lessfs ./examples/master.cfg /sharedir/fuse/

Then i type the command :
# du -sh /data_lessfs/
the result is 145M /data_lessfs/

After that,
I cp some files to /sharedir/fuse/, where is the lessfs fs mounted.
and I rm all files in /sharedir/fuse/ also, then i type the command:

# du -sh /data_lessfs/
the result is 945M /data_lessfs/

why? the correct result may be 145M?
thank you!