Ah -- I have finally figured out how to answer my question

I'll reply, in case anyone else has a similar question in the future, and runs across this thread.

Going to poolcalculator.com, if I enter 1000 gallon pool volume, and ask for borates to go from 0 to 60 ppm, it tells me that requires about 70 oz. of borax (plus acid, of course, to bring the pH back down). That would be just about one entire box of borax.