Can I be vague and say as far as you feel like going?
Really, a lot of it comes down to what you are ready for. I remember last year going longer in 2 runs the day after a long run than I went on the long run itself. I also remember points in time where I didn’t feel like I could run at all the day after the long run.
What I would say is start running tomorrow, warm up, then decide how far to go. I know I always like running the day after a long run to loosen up the legs. Beyond that, you have to decide how far is right for you at your current fitness level.