The voltage divider ratio is designed with the 1.2volt to 1.25volt bandgap feedback voltage of the LM2676 in mind (1/(11.3+1) = 1.2195).
Because that internal bandgap has a bit of tolerance, your 15volt supply can be off a bit too.
I don't see how this should be a problem though.
Old analogue gear with 15volt rails can usually tolerate between 12volt and 18volt.
14.7volt is actually very close to 15volt and shouldn't give any problems.
Leo..