You have 10 days of work, two of which go to planning and retro. Now you have 8. But, is there any kind of testing process before the release? Almost no one has

You have 10 days of work, two of which go to planning and retro. Now you have 8. But, is there any kind of testing process before the release? Almost no one has CD. CI, sure, but CD? Almost never. So if you assume a few days for QA if you have it, now you have 5 days to work. Only, the pointing was done with "T-shirt sizes" without really knowing how to do the work, and you're dealing with code created by this very process, so it is sloppy code, built in a pressure cooker, and you have to understand what the last person did before you can extend it. You'd like to make it better, but then you'll look bad compared to anyone who doesn't roll something over to the next sprint and ships whatever hacks work, however vile. Good luck! My solution is to ignore the deadline and do what's right and explain why, as I go. This will only work with great product folks, not mediocre ones.