How to reduce STU size

cfpddr05-nas1.sldc.sbc.com:/backup/src_rep/ebr/cfpddr05/csprd211/nfs_stu001 6805                                                             9915776 66940254720 1119661056    99%    /opt/app/ebr/cfpddr05/csprd211/nfs_stu0                                                             01
cfpddr05-nas2.sldc.sbc.com:/backup/src_rep/ebr/cfpddr05/csprd211/nfs_stu002 6805                                                             9915776 66940254720 1119661056    99%    /opt/app/ebr/cfpddr05/csprd211/nfs_stu0                                                             02
 

If it is "nfs_stu0" how to reduce the STU size.I couldnt delete, if it iis nfs.

Please someone give idea.