I put an email to Uderzo. i think small folders are not considered. But my folder contains two important dwg files. So I think is not a good space sniff.
Small folders are considered, but not necessarily shown on video due to the small screen area. However, their size is considered in the computation of the parent folder size.
You may want to try lowering the "Min element size" parameter in the configuration dialog to check if the small folder appears. If it doesn't appear it means it's too small (consider that the main purpose of SpaceSniffer is to find big elements, not small elements) but, still, it is considered in the parent size. It's only a display "issue".
You may want to check it by using the File/Export function. This function will export each filtered item, even the smallest one.
In next version (188.8.131.52 few days to release) there will be more filtering/exporting capabilities. I'll try to squeeze into the new version also a "filter by folder name" function.
Let me know if this is of any help.
Greetings! Umberto Uderzo