Plug in SEO

Every email I receive or update I get from PluginSEO it says that my SEO is 100%. Now my website is quite busy and has been around for many years, but when I changed Platforms to Shopify I pretty much had to start from scratch and build up my SEO, which is obviously not perfect as I only starting doing this 3 months ago. Now we all know (or should know) that onsite SEO can take years to build, but apparently mine is perfect all the time. I do get about 30K+ visitors a month but I reckon my SEO could be better, but with this app telling it's perfect I don't know where I can improve things which is the whole point of the app in the first place.