reducing space between punctuation in xeCJK

I try to reduce the space between the dot and the apostrophy in xeCJK:

There is a detailed manual but I cannot read it. Is the manual available in English somewhere and if not, could you please help and say which of the commands are doing what I want.

\documentclass{scrbook}

\usepackage{xeCJK}

\begin{document}

Chris，我们认为David看见了。'

\end{document}

• For single use you could try \! before the apostrophe. – Marijn Apr 19 '18 at 10:52
• No, the manual has lots of stuff: LongPunct, PunctWidth and so on. But I do not want to do lunatic stuff that has side effects I do not understand. – Stefan Müller Apr 19 '18 at 13:10
• OK. Google translator actually produces usable output. So I can understand the manual now. \xeCJKsetup{PunctStyle=...}` seems to do the job. – Stefan Müller Apr 24 '18 at 8:01