Hi. It means that your static file headers are already inserted, for example by some other plugin you use for optimization, or they can be directly written in htaccess.
Thanks for the responsiveness. I don’t see that green tick in the screenshot above, I get this:
“Browser static file caching headers are currently disabled. Follow this link to read the article about how to enable browser cache with your server software.”
I did ask the hosting company to help and they have done this in the htaccess file as you remarked, so i guess all is good despite what the plugins are telling me.