Need Help Writing a Dated Difference Formula

I have a txt file brought into PowerBI via a sharepoint folder, and its a list of transmitted documents and the dates in which each transmission happened. I don't necessarily care about all of the correspondence that happened back and forth with these documents. I only care about the earliest date and the latest date, so i can come up with a dated difference.

Below is an example of the type of data i'm working with. The rows colored in orange and red are seperate packages (i can tell that by the description/submittal ID & the Sequence column). There are dates inbetween the first and last date, but I am unsure how to ignore the data in the middle of the first and last dates.

Any help/advice would be appreciated. Thanks!