It is actually possible to fix this blur issue. Just adjust the sharpness and detail of the photo. But there are a lot of difficulties with this, since you need to do all this in Photoshop, make, save, set a normal format, and so on. Although I usually instead of photoshop do it on
https://www.softorbits.com/unblur-photos/ to make it much faster and I could post normal photos on kickstarter. By the way, I'm not particularly sure that there is exactly 620 because, if I'm not mistaken, I found both 680 and 580. But this is not accurate, so I'd better trust you.