Shouldn't there be a take off distance chart somewhere, and that's how you figure it out based on conditions and weights?
Read the original post. There is a take off distance chart for 10 deg flap, but no chart for 0 deg flap.
means there is no requirement to refer to 6.1 and 6.2 (factoring 15%) if using an approved foreign flight manual.
you can use the tables in the manual without having to factor 15%
Figures in the flight manual are "best case", new aeroplane and skilled test pilot. Adding 15% is a sensible thing to do, you would be crazy not to.