Hi Sanin,
What balenaEtcher version are you using? You may see the version number after clicking the cog icon on the upper right corner.
balenaEtcher rewrites the partition table on the disk based on the image being written. This makes it seem that the rest of the disk is unusable. If you want to reset your disk to make the partition table span the entire disk, you may follow the guide below:
Most disk utility GUI tools only reformat the disk based on the existing partition table it has. If you wrote an image to the disk which has a smaller partition table size, the rest of the disk seem unusable. The guide above should fix this.
Regards,
Carlo