For WD, the testtags.php is used for all the almanac data. You can't edit that file directly to change values as it is created anew by WD from the tags template file in c:\wdisplay\webfiles\testtags.txt at each FTP upload interval.
To change WD data on your site, use WD, View menu and change values using the Averages/Extremes and/or the All Time Records buttons to open the dialogs to do that. Since you didn't specify what values you were concerned about, I don't know which of those two dialogs would address the data issue.
Hope this helps...
Best regards,
Ken