Example:
<max_entry is_neighbour="false" />
<max_entry is_neighbour="true" />

The game selects ALL the factions

<max_entry is_neighbour="true" />
<max_entry is_neighbour="true" />

The game selects only the factions that share borders with the actual faction processed

<max_entry is_neighbour="false" />
<max_entry is_neighbour="false" />

The game selects only the factions that don't share borders with the actual faction processed