Error Message:

The selected users have different Logon Hours settings. You may edit these settings, but they will be initially reset. Do you wish to reset and edit the Logon Hours settings for these users?

Explanation:

You have selected multiple users who don't have identical logon hours. Before these hours can be edited properly, they must be reset to the same initial state.

User Action:

If you do not want these hours reset, you must edit the logon hours of each user individually.