If the numbers are not correct, then the YTD 1099 fields on the Vendor Statistics page are editable - provided that the option to Edit Vendor Statistics is enabled in the Company Profile. This field is not being calculated from anywhere else (it is just an accumulated value), so if you know what the number needs to be, you can simply overwrite the incorrect value with the one you need.

If you have to do a lot of changes, it might be faster to Export Vendors (just the Vendor code, Name and YTD 1099 fields) to an Excel file, change the 1099 values to correct, then import that file (overwriting the bad values).
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And just to be clear with what Doug posted: the Print 1099 forms is a specification, not a Crystal report, meaning it cannot be edited and placed in a separate directory for customization. The Vendor Transaction report can be customized to include a filter for those that track 1099s - of course if you want to turn off that filter you have to modify the report again. Edited reports in versions of Adagio prior to 8.0 are stored in the 'root' \softrak\xxWin directory (replacing the original report). Edited reports for Adagio 8.0A or later applications are stored in the \ModRP sub-directory (which you may need to create manually).