Duplicator is not working as accepted

I am duplicating an imagePlus with specific number of slices but the results shown is not as I expect,
original image RGB with 8 slices,

ImagePlus imageDuplicate = new Duplicator().run(imp, 1, 3);

Tested with ImageJ Macro and used the command IJ.run as follows in Java,

IJ.run(imp,"Duplicate...", "duplicate range="+String.valueOf(firstSliceIdx)+"-"+String.valueOf(lastSliceIdx)+ " use");
IJ.run(imp,"Duplicate...", "duplicate slices="+String.valueOf(firstSliceIdx)+"-"+String.valueOf(lastSliceIdx));

It duplicated the whole stack and not only the slices indicated.

The following code is recordered when I duplicate slices 1-3 of a 3 channel, 8 slice hyperstack, and it works as expected.

imp2 = new Duplicator().run(imp, 1, 3, 1, 3, 1, 1);