Sleep question

I have a question, and I’d love it if you left a comment here on my blog about the following:

I’m sure this has happened to all of us, and by no means am I complaining or regretting this in any way. I went to bed around 10:30pm last night or so, and my phone rang around 2:15am this morning. It was one of my best friends calling to ask me to pick him up in New York City due to the NJ Transit trains no longer running. A friend was in need, so naturally I said I’d pick him up no problem. Thankfully he offered to take the PATH over to Jersey City so I didn’t have to drive as far, but I managed to pick him up and get home by 4:15am. I’m glad I was able to help him get home safely due to there being no trains back. There used to be, at one point, but after a schedule revision there weren’t any past 1:00am. Oh well, no problem at least we know for next time.

The question I have is this: If I went back to bed at 4:15am, and woke up at 9:30am, how much sleep did I actually get last night? 10:30pm-2:15am, then 4:15am-9:30am. Combined it’s 9 hours, but they weren’t 9 continuous hours. There was a 2 hour break in the middle. But, as I’m sitting here writing this, I don’t feel like I slept for 9 hours. I feel like I slept for, maybe, half of that. Since there was that 2 hour period in the middle does that nullify the sleep I got before hand? Maybe things will change as the day progresses; I’m sure as I get up and about and doing stuff I’ll feel more awake, but I have a few other things coming up in the next few months that may bring about the same sleep schedule and thus I figured I’d pose the question, and I’d love to hear your thoughts.

By the way, good morning. :)