Why was the device name added when converting the OVA image file using virt-v2v?

Issue

• When I convert an ova image using virt-v2v, the file is created with a disk name after the image name.

# virt-v2v -i ova test_vm.ova -o local -of qcow2 -os ~/result -on test_vm.qcow2
...
# ls ~/result/
test_vm.qcow2-sda  test_vm.qcow2.xml