Basically, your full name, e-mail address and mobile phone number is the only information to be indicated in Form G-1145, E-Notification of Application/Petition Acceptance. You need to provide this information in order USCIS could send you an e-notification confirming receipt of your primary application/petition. In case you do not need such electronic notification simply do not submit Form G-1145.
If you are a domestic customer provide your mobile phone number in order to receive the electronic notification in the form of a text message, or provide your e-mail address to get the electronic notification in the form of an e-mail message. Or you may provide both to receive both text and e-mail messages. Meanwhile, note that an overseas customer may receive only an e-mail, so there is no need to indicate mobile number on Form G-1145.