Why does AVI2DVD not process multiple files?

I tried to author a DVD from 11 AVI files, named as such

blah S1 D1 1.avi
blah S1 D1 2.avi
blah S1 D1 3.avi
...
blah S1 D1 10.avi
blah S1 D1 11.avi

and subtitle files named similarly,

blah S1 D1 1.srt
blah S1 D1 2.srt
blah S1 D1 3.srt
...
blah S1 D1 10.srt
blah S1 D1 11.srt

I followed the instructions in this article, where it said that AVI2DVD will process multiple AVI files as long as they have the same file name with "1" and "2" etc. added at the end, and that the same goes for subtitles. When I selected the AVI input file I selected the first file ("blah S1 D1 1.avi") since it only allows you to select one file. Similarly, I selected "blah S1 D1 1.srt" for subtitle input. However, when it authored the DVD, the resulting .VOB files only had the contents of "blah S1 S1 1.avi", not the other AVI files.

What am I doing wrong? How do I get AVI2DVD to process all 11 AVI files? Is it because I did not name the files properly? Or does AVI2DVD allow you to select multiple input files in some way that I'm not aware of?

Thank you in advance for your help.