Possible error in foot vs meter conversion for "Good Sound Room Volumes" Chart-Acoustics Forum-Acoustic Fields Forum

Looking over the optimal room sizes, I saw two images that you present (one with dimensions in inch and another one in metric system). Coming from Europe (where the metric system is used) I believe there is an error in your conversion from foot to meters.

9′ is about 2.7432 meter, not 2.43 meter as presented in the image. And so on, all of the conversions are in error.

Am I missing something or is this an error?

Best regards, keep up the good work!