Anti-defacement how to compare different

use Anti-defacement to protect website, but has strange things happen, some files did not be modify, FortiWeb restore these files and send alert mail.

can some one to tell me how to compare different between base and website file.

1. on website generate a Excel report use template file to fill data

2. popup download page

3. download file

receive alter mail, but the template file did not has any modify,even create date, modify date.

thanks!