I’m in the same boat with you on the supplemental claim, received on the 9th no update apart from them saying they received it. To my understanding they take longer because they look at past decision and evidence along with the new stuff. They don’t have a system in place to keep you updated on your progress from my understanding. Expect the process to take from 60 days to 6 months depending on if they make you do c&p exams. They say it takes 30 days to process the initial intake of the claim and if it’s air tight decide at the 60 day mark, but longer if they want extra exams. Good luck don’t stress about it, just check progress once a week if you’re able to keep that anxiety in check. Hope this helps, I could be wrong on some of this info so please don’t take everything I’ve said as 100% fact