This rule is only applicable during the Enemy: Sail a Boat action.
After the Chieftain Boat ends its sail, it then Deploys Settlers from its Clan Mat onto its current Island. It does not pay Food to do this, instead deploying the number listed for the Sail action and not counting the additional Chieftain Sail. For example, for a "Sail x3", it would deploy 3 Settlers. If there are not enough Settlers on the enemy’s mat, it will take any remaining Settlers from another Island where it has the most Settlers. If there is a tie for most, choose the tied Island where your influence is least. If there is still a tie, you choose which it takes them from.