It may be best to ask the specific manufacturer.

The valve plate must be a little bigger in one dimension to close off the valve. The width will be the same but the lenth will be slightly longer if it is a rotating plate. It will be larger all around if it is a stop plate that rests on the body flange, and it will be the same diameter if it is a plug.

That's my guess since you didn't say what type of valve you were talking about.

Why don't you post a screen shot of the sheet that has those dimensions and some explanation of what type of valve it is, so we can comment on what you're actually dealing with?

Valve sizes are usually referred to the ends to welding/bolting to the pipe and usually are the NPS (Nominal Pipe Size), for example 4" or 6".

Unless it's a butterfly type, the most common "control" valve type is globe one. The size of the "central" part or "body" valve part (where the trim is in) use to be in the order of magnitude of ends diameter, but it's sometimes greater.

Kind regards