While setting up an AD sync job, you may wish to ensure that the LDAP filter is only going to pick up the entries you expect it to. The filter can be tested as follows:

• Open up the Active Directory browser on your Domain Controller
• Right click on your domain (such as example.com) in the left sidebar
• Select 'Find...'.
• Change the search options to Find: 'Custom Search' In: '<Your Domain>' or 'Entire Directory'.
• Enter the LDAP Filter inside the Query box and select 'Find Now'.

The Search Results will show you what results are found from that search. If a device or user appears in this search and in the OU specified in the Sync job, then it should be picked up by the Sync job.