Typo fix

Thanks to Dominik Honnef for spotting it.
Fix numbers from example

Thanks to Dominik Honnef.
Update ledger3.texi

Fixed typos and clarified CSV import behaviour with regard to column headers (I haven't checked the code, but I noticed the programme behaves this way).
Update ledger3.texi

Improved wording
Merge pull request #327 from myqlarson/patch-1

Update ledger3.texi