Changing the background overlay on one section on mobile only

Site URL: https://triangle-keyboard-t5hz.squarespace.com

Hi - I am changing increase the overlay opacity on the top image on mobile only. This is the code I am using without success.

@media screen and (max-width: 640px) {
 [data-section-id=“609aa62a18656e56660631b2”]  
.section-background .section-background-overlay {
opacity: 0.3;
  }}
 

If anyone can tell me what I am doing wrong that would be great. I am getting a syntax error on the [data.. ] section. 

Thank you.

Password: WLAC

use this code

@media screen and (max-width: 767px) {
    [data-section-id="609aa62a18656e56660631b2"] .section-background-overlay {
        background-color: rgba(0,0,0,0.9) !important;
    }
}