Hi,
I would like this measure "Duration before first assignment" in Business Hours.
For now, i start with this formula:
DATE_DIFF(First assignment of ticket - Horodatage], [Created tickets - Horodatage], "nb_of_hours")
But I don't know how to add this value.

I'm afraid there isn't another solution available at the moment apart from the one my colleague mentioned. Our suggestion for now is to convert that data into calendar hours.