You also need to set the options to allow diminished intervals. Presumably, the interval between the sharpened third and the unsharpened 6th is a bit hairy.
The only way I can get the figure to behave the way you want it to (unless the key signature has at least three sharps) is to type the following: !6,s.
The chevrons around the n hide the natural sign. Oddly, when you re-open the figured bass popover for that figure you will see this: !6,#<3>, which is what should have happened when typing !6,s - but it doesn’t for some reason.
Thank you, @benwiggy ! This did the trick! ( It’s quite surprising that if the option ‘allow diminished intervals’ is not chosen, then ‘follow input literally’ does not follow input literally. Oh boy.)
@tbabcock123 , thank you very much for your response. I have to report that in my case, before I ‘allowed diminished intervals’, your proposal also sharpened the sixth!
Those are Engraving Options (which thus specify how something appears), rather than Note Input Options (which controls how you enter it/how it’s interpreted).
The Engraving Options set the appearance of unmodified figures in diminished intervals. The Note Input Options is all about what you mean by what you write when there is a diminished.
Oddly, when I typed the figure as shown in the top screenshot of my answer to you (! chevron then n then chevron then 6, s) the forum software removed the chevroned n!