Why do my iTunes take up so much space?

I own an iPhone 5s. I was told that I should be able to keep roughly 2500 songs on my phone, but it can't even hold 1400 at 128kbps. I have 64MB of photos, 1.37GB in apps, 513MB in books, 79.8MB as documents and data, and 1.59GB as other. Was I lied to or is something wrong? I've already looked for info on my problem but nothing I found helped.