If what you're referring to is DIST and ARR...you may not be able to "reset" to zero without pulling the negative battery cable. Do check the operating booklet for the MID (if you have one)...or download one in PDF format (if you don't). Sites like e38.org and its e39 sister site should have MID operating manuals at the bottom of the left column that you can download.
You may need to NOT use those two features if you want to see "0" when you press the button to bring them up. If memory serves me correct...once they've been used...they usually continue to count down...going into negative numbers unless you constantly reset them or use them for another distance/arrival calculation. I would only use these features if I needed to know how long it will take to get to a specific location in consideration of other factors like stops/starts/slow traffic/heavy traffic/traffic jams/clear roads/etc. For instance, if you were running low on gas...and you pass a sign that says the next fueling stations are 75 miles away...you could enter this data in DIST...then the ARR feature will approximate the time you'll arrive at that point.
"Journey mileage" would be "trip odometer" in my head. The use of DIST & ARR I would use for a slightly different purpose.