Hey Steve,
No this is not what it means. What it does is take the data you are using and it changes a % of the total bars by a % ATR change.
Defaults are both 30% so if you are using 10k bars of data then a random 30k of the bars will be have the open prices modified by a 0-30% of the ATR at that time in the data randomly.
Essentially simulating using similar but slightly different data.