Google OA intern extension

Ive never asked for an OA extension, so not sure if I should ask or does it make a candidate look bad if they ask for an extension? I have an intense work schedule with a masters class where I have a new paper due each week. I haven't had time to touch leetcode at all and quite frankly don't think I'll perform well. But at the same time the OA said: "To keep our process fair, we ask that everyone complete the coding exercise by the deadline. If you have a scheduling conflict that absolutely can't be moved, let us know as soon as possible by emailing"

Any insights? Is asking for an extension makes you look like a bad candidate? Do I just take time off work to grind leetcode?