Any field that requires input on an edit page must have a value to submit the page. If it is left blank, the page will display an error on submit. There are 2 methods for avoiding this error.
1) Edit the alert settings through the Test Admin section. This is done through the following steps:
Log in and navigate to ADMIN tab.
Under Test Admin, click Add/Edit Backbone tests.
Select the tests you need to edit and click Edit.
In the Alert Settings section, choose only the items you want to edit or configure and then click Continue.
Edit as needed and click Submit.
2) Enter random values. If the alert is turned off, the set threshold will not have an impact. If you enter any value, you will be able to submit the page seeing all settings without the error.