Why is there an extra 었 ?

[imaBALLER]

Lately I have had some trouble with the past tense of some verbs.

그냥 인사 하러 왔어요. I just came to say hello.

너 가자마자 민수가 왔었어. “As soon as you left, Minsu came.”

그 남자 언제 갔어요? When did he leave?

한 달에 한 번 갔었어. I have visited once a month

Why is there an extra 었 ?

[julialim]

Hello~~

For example,
한 달에 한 번 갔었어: I used to visit once a month.
This sentence means "I don't go there thesedays."

But It has another meaning.

너 가자마자 민수가 왔었어. “As soon as you left, Minsu came.”

"었" of this sentence emphasizes the fact of "Minsu came".

If I make a situation of this sentence,
we had a party last night. And you say " eventually, Minsu didn't come last night."
I say,"너 가자마자 민수 왔었어."

Does it make sense?
I didn't notice "었"before as I use it at all times.

[imaBALLER]

Thanks Julia,

It seems like a subtle difference,I will pay attention to it in the future.