Not sure why you want to apply 30 days before if it not necessary. If you parents get COPR during that time you can land if you can go to the US border. Would recommend applying for the extension near the end of their supervisa expiration date.It’s very hard in my case, my parents application is in New York and I’m not sure when they will reopen their visa application centres as they have been hit massively. Can I apply before 30 days ? But the processing time is 90 days that’s why I was taking precautions.