A report created on the phone can be edited on the web as well (and vice versa). Save the report on the mobile and then login to the web and go to your home page. You should see the report there. You can open it and edit. 

1) The following screenshot is showing the report saved on the mobile under Main Menu -> Reports

Note: Make sure the report is Saved on Device and Web (shown in the green background in the screenshot below)

2) The same report can be edited on the web application by going to the Expense Reports link from the main menu and then clicking on the Report Name shown in blue text below