From above link:
With Azure AD Sync, you can remove individual attributes from being synchronized.
Some services might not behave as expected when certain attributes are removed. The affected attributes are listed with their Active Directory LDAP name in the Install the AADSync Service.
There are also some attributes that might be listed with a different name in other interfaces. For example, the attribute l from Active Directory is tracked as city in Azure AD.
Follow the link on top to see the full article, it is very useful.