The frame counter is being taken off. Do this procedure while the rear cover is open.
6 x 6	24 x 36

There is an unique function only for Rolleicord Va and Vb that 4x5.5cm format, 4x4cm format and 28x40mm format (all of them are 16 exposures.) are available with this other than 6x6cm format (12 exposures) by means of the picture-size switching adapters and also 35mm film (20 exposures) is available by means of Rolleikin.
Take off the frame counter unit by turining the screw in the middle of the frame counter while the rear cover is open. And then attach adapter for each format there.
When using 35mm format, switch the format by depressing the film pressure plate, and at the same time sliding it. (In the pictures show the direction for each format.)