SNS
plus ten percent of the total fuel burn for the Class II portion
I think that is where the major difference is between our different ways of determining fuel required.
We used to use a fixed % which 5% for short flights and 3% for long range flights with en-route alternates.
We now use Statistical Contingency Fuel based on gathered data for that route and flight number. That means that some flights get a generous amount of CF (maybe up to 10%) whereas some flights get less - typically long range flights arriving at quiet airfields or before the LHR rush.
As an example, I came back from the Far East into LHR recently on a B744 with a 10 hour flight time, we had trip fuel of 103tonnes + 2tonnes contingency (95%SCF) +3.9tonnes div +4.4tonnes reserve +0.7taxi.
We landed with 8.3tonnes (~18250lbs for our US colleagues) having burnt the contingency fuel holding at LHR, equating to 49 minutes fuel in tanks. So it all worked out nicely on a cavok day. Loading extra fuel would have been my call, I would not have needed to give anyone a reason, but on that day I was happy.
[Note: not trying to point score, just for amplification and interest]