I've rewatched the episode in search for iconable moments, and have some thoughts to add to my review.

• Ooh, the things you observe in rewatches! I just noticed that when we fly past Level 1056, it's still whole. No smoke rising from anywhere. The Master could have arrived the same moment Doctor & Co. did.



• Hee, I just noticed that Razor did the eyebrow thing. That raising of the outer part of the eyebrow that I've noticed during my recent Life on Mars rewatch.



• So I calculated the time difference between Levels 0 & 1056. Not that I should have tried, because 1. the information isn't reliable and 2. I'm math-challenged.
  
  The first time we see the displays, the numbers are:
  

  days	hours	minutes	seconds
  2	10	45	17
  365034	12	31	0

  
  The next time they show:
  

  days	hours	minutes	seconds
  2	10	45	17
  365036	0	23	25

  
  Those displays are really helpful for orientation, but why are they there? Did the builders expect a the ship to have run-in with a blackhole? Or what other timey weirdness could it meet?
  
  Anyway, the time on the bridge hasn't changed, while one Level 1056 1 day, 11 hours, 52 minutes and 25 seconds have passed. That's 129145 seconds, which should then be how many times (at least) faster Level 1056 is than Level 0. But since we haven't seen the bridge's seconds change (and what time that was in Level 1056), it's hard to tell exactly.



• Ooh, while Razor explains the time difference there's a Mastery soundtrack that now makes sense to me.



• "He's been raising that eyebrow for a week." The eyebrow lasted 3 seconds at most, so that could last for at least 4 1/2 days in Level-1056 time.



• *sigh* When we see the displays again, for Bill a bit over a year has passed, but they're not helpful at all for calculating a more exact difference between the levels, because the bridge clock went back 17 seconds! And this is why the information from the displays in unreliable.



• Oh and when exactly were the clocks started? How much later did the time weirdness start? The janitor spoke of 2 days ago and the clock is showing 2 days. I expect the clock was started when the ship left the builder's yard and just some hours into the journey it had its run-in with the black hole. But if we don't know how many hours, we can't calculate anything from it.



• Seriously, I can't get over the fact that for a decade Bill and the Master were best friends, colleagues and roomies! Hey, it looks like Razor sleeps on the sofa, so Bill can have the bed. That's some spectacular staying-in-character from the Master!



• If not a even a whole second passes in 2 days, how come Bill is surprised to see what she saw on the monitor? When did she last check what the Doctor & Co. were up to?



• "But it's been 10 minutes, so she must have been down there for years." That should be at least 2.5 years.



• Finally I'm thinking about floors! Okay, so if that ship is 400 miles (~644km) long, a floor can't be more than 609.6 meters high. It has to be less, because there are also thrusters and ceiling/floor thickness and whatnot.



• "It took me a while to work out who you were." Yeah, so how did he do that? How could he work out Missy is his future incarnation?



• Oh, was that part about 10 years having passed only in the next episode? Anyway, 10 years on Level 1056 are about 41 minutes or a bit longer on Level 0.