Probably only a couple of days. Some people actually do an intentional carb refeeding day (usually athletes or weightlifters) so it’s not like it’s going to totally destroy you.
Don’t get so fixated on single weigh-in checkpoints. I do suggest you go ahead and weigh in and record it if you do that, but then compare it to the next two weekly weigh-ins.
It is quite common during weight loss to have stalls, plateaus, and even regains over short periods, before loss starts up again. There is often a time lag of several days or even weeks between your actions and the results.
Don’t get caught up in thinking every week has to be a linear improvement.