How to calculate total PEM in Qualitivity if a translator changes segment more than once?

A translator post-edits a file pretranslated with MT. How to calculate total PEM - between MT proposal and the final translator's version - if the translator changes segment more than once?

I can imagine at least two cases:

- Segment was visited two times, once changed, once not. This is trivial - the PEM should be taken from the record where translation was changed.

- Segment visited two times and changed a bit each time. This is non-trivial Slight smile