usage of particle と in this situation

Question

So I came across this phrase:

友達と４人で一つずつ弁当を買ったら。。。

So what does 友達と４人で mean? A friend plus 4 people? 4 people who happen to be friends? With the friend they are now 4 people?

I have never seen this construction, usually it´s either 友達が４人で or ４人の友達で that I encounter, hence my confusion. Any help would be appreciated.

Answer 1

友達と４人で means "With the friends they are now 4 people", that is to say, they are I and three friends.

何人 in ～と何人で means the number of I and ～". For example, 彼女と二人で映画を見た is translated as I saw a movie with a girl friend.