From the WordPress dashboard click on 6storage -> Settings.
After selecting the settings you will be landed on the tenant portal setting page.
To customize for your business requirements click on Feature customization you will find Fields, Additional addons & other operations.
By enabling the unit size will display the unit size
Ex: Width x Length (or) Width x Length x Height
In the below image you can see the WxLxH, As an example.
By disabling this option the sizes will not be available.