High open tables set.

In my current database, I have 100 schema with 350 tables in each. Ive set my open table cache to 210,000 and the performance of my database has been stellar since this has been done. The problem I am running into his mysql seems to be using more memory than I allocate as per my innodb settings. So my question is does having a high open table cache cause to mysql to use more memory? I currently allocate about 230GB to innodb and my server has 512GB of ram. My db instance has been running for 30 days now and mysql is using about 340GB of memory and growing slowly.

Thanks for any information that can be provided.