Both Telephone number and Mobile number are not required, but recommended. Also currently Telephone number can be both Australian and foreign. But "Mobile" should have strict pattern 04 xxxx xxxx

Actual international mobile number:  +49 17654321123

As per ATO, provide this using IITR579 and IITR50. Using this will ensure the country codes and area codes are provided correctly.

IITR579 Daytime phone area code

IITR50 Daytime phone number"

Note: This field is not required so it can be also empty.