Uncheck both the 'Show dimensions' and the 'Show room size' fields and click on 'Save'. The measures are hidden now.
When you click again on 'Show room size', the total square meter/feet for each room will be shown. Also in the down left corner you can see the total square meters/feet of the plan.
Uncheck again the 'Show room size' and click on the 'Show dimensions' - only the length of the walls are now visible on the plan.
You can also move the measures when, for example, you have a furniture piece that hides them. Simply click on the the middle of the measuring line and move it in either direction.
Please note that these changes in the Settings (i.e. 'Show dimensions' and 'Show room size') will not be saved to your account and will be lost when you logout.