-란다 delivers a piece of information in a knowing, slightly storybook voice, the way an adult explains something to a child: 인사는 그렇게 하는 거란다, 재성아 'that's how you say hello, Jae Sung.' In these lines it lands on a fact or a life lesson the speaker feels entitled to state. One line uses a different -란다: 가란다 means 'they're telling me to go', relaying somebody else's order. The 오란다 in the last line is not this ending at all, just the name of a snack.