Hello Madhu1,
The size descrapancy between the source and destination volume is due to the source volume most likely already having space efficiency features already taken into effect. The destination volume either doesn't have the same efficiency settings as the source or the efficiency jobs have not completed on the destination volume.
Reference document:
Display a list of volumes with efficiency
Viewing efficiency space savings
Using deduplication, data compression, and data compaction to increase storage efficiency
KB: Snapmirror Destination volume space usage is greater than Source volume
KB: Why is a destination volume on SVM DR smaller then its source volume
Regards,
Team NetApp
Team NetApp