It’s not relevant where a grey card midtone is located - it’s just relevant what you think should be midtone in your image. Because this is kept constant in filmic.
Unless you are editing images of your greycard 
It’s not relevant where a grey card midtone is located - it’s just relevant what you think should be midtone in your image. Because this is kept constant in filmic.
Unless you are editing images of your greycard