The Divi Theme comes with a range of header formats, including two "centered" layouts. When viewing these centered layouts on mobiles, the header menu is shown along with the "Select Page" text, e.g.
If you'd like to remove or change this text, there are a couple of options.
Hiding the "Select Page" text with CSS
If you want to remove the "Select Page" text entirely, you can do so by adding CSS to Divi, as follows:
Changing the "Select Page" using PHP
If you're comfortable adding PHP to Divi, you can replace the "Select Page" text with text of your choosing with the following code snippet:
Removing / Changing the "Select Page" Text with Divi Booster
Divi Booster now includes an option to change the "Select Page" text. The option can be found on the Divi Booster settings page under Header > Mobile Header > Change centered menu "Select Page" text (Divi Booster v2.7.0) or under Header > Main Header > Change centered menu "Select Page" text (Divi Booster v2.2.9 – v2.6.9):
Simply check the box, enter your new text (or leave blank to get rid of the text) and save.
The result will be a menu which looks something like this: