I am having 3/4" solid prefinished maple installed and do not know
what percentage beyond the measured 600sf would be advisable.
The floor is being installed straight not diagnol.

Any information is greatly appreciated, since i have been told a range
of 0 to 10% over the 600sf.

Thanks for any advice

5% is standard, and I rarely use that up.

It is always a good Idea to have several boxes left over after the installation is complete. That way years down the road and the unexpected mishap takes place, you won't be on an endless search for acarton or two of discontinued wood flooring

Amen to that! I am often asked to repair/patch floors that have been discontinued. It is almost impossible as the profiles of T&G are changed, the colors are changed or the flooring is just no longer made. Having a little extra can really save you down the road.