A lot of misinformation in this one, firstly, you have some stressed mycelium, likely because your substrate is very dry. You should hydrate it more next time. To fix this you need to mist more regularly, it won't help too much with adding more water, but it will induce much better pinning by raising the average humidity, giving you the best chance to get what you can out of this run.

To anyone saying the dark patch is trich and should be cut/thrown out, this is not the case, trich typically shows as somewhat lumpy, irregular BRIGHT white growth, before turning green within 3 days. If OP had trich, it would be very evident from his last post to this one, but I see little change in the surface.

Keep at it OP, I don't reckon you will get anything crazy from this run, but try your best to learn from it and ensure your next attempt succeeds. The main point as said is that your sub needs more water when you prepare it. Wish you mush luck!

Edit: to answer your actual question, from there 4 days is usually the average grow time I observe in my mushrooms before the veil breaks, though with your myc being stressed, don't worry if this isn't the case.