This article explains the purpose of the "Strict" checkbox located within the Carrier -> Hierarchy settings and how to use it. The strict checkbox is used when you want to enforce the selection of the hierarchy information from the Edit Hierarchy list.
The search field should be used to locate the desired information. When found select Apply to add the selected info the hierarchy row.
Please note: If you want to be able to enter any desired information into the hierarchy the strict option should not be used. Please also note that this option is setup per carrier hierarchy scheudle and when used only applies to the selected schedule.