Once again:
DRIVES DO NOT HAVE LESS CAPACITY THAN ADVERTIZED.
Drive advertizing uses the abbreviation "GB", which denotes THE DECIMAL UNIT. So you can expect your "200GB" drive to have 200,000,000,000 bytes, no more.
As pointed out above already, the wrongness is in fact on the other end - 200 GB are about 186 GiB. If your software shows that as "186GB", then the software is bull not the drive advertizing.