I'm not an expert but have worked in these kinds of environments on and off over the years.
It's hard to offer broad advice as every encounter is different. Your workplace might offer training though to give you some tools, which will likely also teach you the things not to say (eg promising a result, stoking the fire, preaching, etc).
Calming someone down isn't always the goal either, sometimes people just need to process difficult information or grieve for the loss of a loved one. All you can do in this situation is to offer a safe place to do that, and maybe a sympathetic ear if they need to talk, and perhaps to validate their feelings. Otherwise just being present is often enough, as is knowing when to give someone space.
Came across this which I've not validated but does seem to make sense at a glance: Comparison of WLTP and CLTC
Based on that the WLTP range would be 828-900km (515-560 miles).
Real world, 6-700km at a guess?