Easy
I am assuming that you are a student PPL from your profile, so forgive me if this is incorrect.
All of the figures quoted in the thread seem reasonable, given differing circumstances.
If I were you, I would get the POH and study the info for yourself.
This is because you will learn a lot about the variables - % power (and the rpm to achieve this), altitude etc.
And remember, the POH will usually say something to the effect 'with the engine leaned per the manufacturers recommendations.'
If you don't understand what this means practically (and there is no shame if this is the case, as we tend to fly fully rich in the UK when doing our PPLs), then talk it over with an instructor as the reduction in endurance if you are not leaned out appropriately can be very significant.
Hope this will be of some assistance.