Hi David,
I'm pretty sure you won't find a reference to RPT flights in the exam, I never saw one, but if it says charter (and 99%) of them do, you need to add 15% variable reserve. Make sure you calculate it the way Bob says in the books otherwise you'll end up with an incorrect figure.
For example, 100L at start up, 20L fixed res, 5L taxi = 75L usable. 15% of 75L = 11.25L, so usable is 63.75L. I tried it this way a couple of times but.. percentages can get tricky.
If you do it the proper way, (100-20-5)/1.15, you get 65.2L. I know thats not what you're asking but I found I did it wrong a couple of times therefore the answer I got was off, so make sure this step is done right.
As for fuel flow, this will be in the text of the question. "Fuel flow for this flight is 80L/hr" or something, it will also either give you the fixed reserve required, "Fixed reserve is 50L". Or "Fixed reserve is 45 minutes calculated at cruise rate (which it would give you)" You won't need to assume anything in the exam.
Also look through the whole question text for the word Charter, it could be right at the end say after they have given you the fuel and distance and ETI and everything, at the very end they might ask "How much fuel is required at start up for this Charter flight". An easy one to miss.
Minimum fuel question
<--- if you have a look here I did ask Bob the same question with regards to minimum fuel. I found in the actual cyberexam the multi choice options were further apart than the practice exam so if you're on the right track you can catch the answer pretty easily.
Good luck with it!
Michael