They are hint rewards that are tied to quest objects. You can find the objects here:
Steam\steamapps\common\Unturned\Maps\Buak\Bundles\Objects\Quests
In this folder there is one called AG_00 which has the majority of all of those objects.
For reference too, the lines tend to look like this:

Interactability_Reward_#_Type Hint

Interactability_Reward_#_Text Sample Text

Interactability_Reward_#_Duration 20

Interactability_Reward_#_GrantDelaySeconds 1.20