FP Growth - Max Number of Retries Parameter

Hi,

I am new to RapidMiner and have been doing the exercises in the book "Data Mining for the Masses" by Dr Matthew North.
For each exercise I have been trying to understand how each operator works and the underlying algorithms and mathematics.

In Chapter 5 "Association Rules"  I couldn't quite work out why I was getting the results I was, whilst experimenting with  FP Growth.   The issue is around the
"max number of retries" parameter.  The description for this parameter states:

This determines how many times the operator lowers min support to find the minimal number of item sets. Each time the minimal support is lowered by 20 percent. Range: integer; 2-+?; default: 15

After a lot of experimentation and offline calculations, I can only deduce the minimal support is lowered by 10% each time rather than the stated 20%.  Also it seems as if the number of times it is lowered is 1 less than the value of this parameter. ie "max number of retries - 1"  I'm guessing the first calculation at the "min support" value is being counted as a retry; or a coding bug where '<' is used instead of '<='.

Could someone verify the above, or if I am wrong, then how does this parameter work.

Thanks