Sequence distribution over a Dataset

If I’m right, Sequence Distribution over a Dataset is meant to sequentially distribute the selected column value row after row up to the end of the Data set then restart from the very first row of the set so on and so forth up to the total number of rows to be generated. Hence there should not be duplicates in the distributed column unless the generated Dataset counts more rows than the source dataset. How come I’m in the case I should not expect any duplicate but I come up with lots a lot. Is there something wrong with sequence distribution or with me.