Ok, sure I'[m doing something wrong but when I load my route and departure info into FMC and say Simbrief has me departing on rwy 17R. My trip distance shows say 351 miles. Now when BATC changes my departure to rwy 35L I go into FMC departure page and change rwy to 35L now my trip distance is 525 miles. Like it is adding a whole new leg to route. How can I make changes to route. Same thing happens if I make Landing rwy different during flight. What am I missing ? Thanks for any help

Make sure it’s not duplicating any waypoints - sometimes changing departures/arrivals can leave artifacts from the previously selected SID/STAR in the box.

With that said - my DTG on the PMDG 777 has been quite off lately, often by about 50-100nm. At first I thought it’s adding the missed approach sectors to DTG but yesterday I flew into EGKK and it showed 40nm remaining when I was 10nm out when the missed approach didn’t have any distance values attached to it. Not sure if it’s a bug…