C-Class Trip Computer

We've just picked up our 'new' 1999 C240 and have found it's missing the 'Interior' manual. I'm pretty happy with how everything works
except for the trip computer.
When we first drove the car it was displaying the miles remaining in the tank. By pushing the '0' button I've managed to get it to show a trip counter but I can't for the life of me make it do anything else. I'm sure it'll be a combination of buttons or something but if anyone can give some guidance I'd be very grateful.
All we have on the dash is the '0' a '+' & '-' button on the left (which seem to only control the dash lights and a 'h' and 'm' buttons on the right which seem only to change the clock.
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