It depends. Although I'm not 100% sure of how things work in Medina county, I know that the taxable value in Cuyahoga county (where I'm originally from and continue to invest) is based upon roughly 80% of the assessed value. I stated roughly, because certain locales (like Cleveland Hts, University Hts, etc) also add their own millage rates to the county rate. I also know that the taxable value in Franklin county (where I've lived and and continue to invest) is also roughly 80% of the assessed value.
I'm not as familiar with Seville as I am with Brunswick, Lodi, and Medina, but I know that the assessed values differ slightly, but are mostly consistent. So I suspect it's probably similar in Seville too.
Keep in mind that an assessment consists of the value of the land and improvements (or the structure [ie the house itself]). That's why you'll see your tax bill broken down into a few sections, or you'd see the county assessment broken down into a few sections. If you have any questions about the assessed value, or how they came up with that assessment, then call the county auditor's office.