My iPhone says it's low on memory?

I just got my broken iPhone replaced with a new one and I have 300 pictures on it and 5 apps and no music yet and it says it's low on memory? It's so low it won't do the update! It's a 16 GB phone and it says I've used 12.9GB in Settings>General>Usage>Storage I just don't see how that's possible!

I see tons of these iPhone or iPod low-memory questions all the time, and almost none of the people who post them do the most important thing: connect to iTunes and actually see how that memory is being used.

Also left out - whether the iPhone is set to manual management or not. If not, and it's set to automatically sync, then iTunes may reserve as much memory on your iPhone as is needed to hold everything already on your iTunes library.

  • Why is my iPhone 4 memory low? I checked the settings and it says capacity 6.3 GB and available 1.1 GB But I hardly have anything on my phone? 2 songs, 7 videos, 315 pictures and 18 apps. Shouldn't my available space be more than just 1.1? And also, would I lose my pictures and everything if I jailbreak it? And how would I jailbreak it? iPhone 4 iOS 6.1
  • My iPhone says that 7gb of memory are taken up by photos? I only have 161 photos and 29 videos (all average 3 minutes long) in my camera roll. I don't understand how it's taking up that much space.
  • My iPhone 4s says I'm using more memory than I believe I'm. Why? I'm trying to get the new update for my iPhone 4s and it says that I do not have enough storage space because it requires 2.5 GB of storage room. I look at my individual usage and I'm not anywhere close to my maximum storage capacity. I do not know why this is happening.
  • Low memory warning on my iPhone? It's not my iPhone that's telling me I have low memory. It's an application--a game, to be more precise. When I checked how much memory I had, it said I had 12.1 GB's available and only 1.4 used. Is the application just judging my iPhone wrong or what? Should I be worried about my iPhone?