Yes, thanks – the info is still not completely explanatory, but I now see I need to set BOTH the “include” and “restrict” tabs in order to get it exact – many thanks.
What about the other bit of the question – i.e. graph size? If I want to create a symmetrical scatterplot, with both axes the exact same length, how do I do it? I have found the option to set “size” as specified, but, if I set x=y here, it does not give me a square graph …