Purge zero lots

SUGGESTED

I plan to use function Zero lots (FUNSTPL). I run the function in simulation mode and compared the generated log file with entries in STOCK table. 

There were some entries that are still in stock. 

How the function actually works? It is described - that for deletion will go zero lots, but why I get lots, which are still in stock?

What is counted as zero lot? How small values will be considered as zero?