First question: is it realy from google? check with your google account your website and see if the message is there, it might be spam as well......

If not see where google has problems with, to mee your robots.txt looks good.

Else:

This may help?

https://hostingxp.com/resolve-indexed-though-blocked-by-robots-txt/

There is about everythng you need nicely explained.

you can change your robot.txt file in step1 settings -> Advanced TAB -> Seo and Code -> SEO TAB.

But as descriibed it is not a very high priority issue and the  file robots.txt file setting of x5 is pritty standard. You can get more info about the settings by using the button at the end in x5 on the page i  mentioned above.

So Google can't reach all of your pages, it does also not need to, but Google wants to know everything.....

I would not worry too much about it!