Welcome to the Community - There are two reasons why I VMDK would grow -
- The file was configured as a thin provisioned disk - this means the disk will grow as the disk is written to - the down side is it does not shrink automatically - the easiest way to reduce the size of the disk if storage vmotion it to a new datastore -
- The VM is running with a snapshot - this is a delta file that is recording block level changes that are being made to the vmdk - you will need to remove the snapshot to commit the changes to the base vmdk