vyos@test1# set int openvpn vtun20 server mfa totp
Possible completions:
   challenge            Expect password as result of a challenge response protocol
                        (default: enable)
   digits               Number of digits to use for totp hash (default: 6)

vyos@test1# set int openvpn vtun20 server mfa totp digits
Possible completions:
   1-65535              Seconds