Confidence and Paranoia - S1-E5
Corrected entry: In the episode "Confidence and Paranoia", Lister tells us there were 169 crewmen on Red Dwarf before the accident. By the episode "Justice", Rimmer is accused of murdering 1167 people on the Red Dwarf crew.
Correction: There are 169 crew, and obviously 998 people on board who are not crew. Civilian miners? (It's a mining vessel.) Passengers? (Many commercial craft take passengers.) Crew members' families? (They're going to be in space for five years - they might allow families on board). There are many answers, and they all work.
Don't forget the 400 inmates in Floor 13...that's nearly half the unaccounted deaths.