Poor instructions for measuring occular distance: ignore the ones given on the website and get your OD checked by an optician
While my order was shown as 'being processed', I contacted Tenda Glasses requesting to change the occular distance (which I had measured myself, following the advice of Tenda Glasses) to the one I received from my optician. However, Tenda Glasses told me that it was too late to change my order and refused to change it. Now I am stuck with a pair of glasses I cannot use because the occular distance I measured by ruler (as instructed by Tenda Glasses if you do not know your OD) was incorrect.