Ammending logbooks

OK, new question: I put my logbooks (25 years worth) into a spreadsheet
program, and turned up a few errors in the process; mostly due to
misreading my own handwriting. In some columns, the error is as much
as 10 hours. Most of the errors are in my favor. Interestingly, there's
not a single mistake in the total flight time column.

How can I correct my logbook? One way might be to simply put the
corrected values at the bottom of the page next time I total up, but
I worry about having to explain the discontinuity to the next
examiner who's good at math.

Or should I put an entry into the logbook that says "these values
correct for errors in previous pages."?

--
-Ed Falk,
http://thespamdiaries.blogspot.com/