Help with my Iphone

I hook my iphone up to my computer to put songs on it, it syncs, and back it up to the computer and itunes. I go to add songs to it clearly seeing at the bottom on that bar that i have 10GB of space available. I pick out some songs and watch bar decrease in space available, finish, and hit sync. It comes up saying that I need 8.2GB of free space in order to sync the music. I haven't had any problems with it up until now. I usually have it full but the update to the newest IOS deleted my songs and I had some spare time and decided to put some music back on it. So I clear up the 8.2GB it says it needs by taking photos off it and putting them in a folder on my computer and deleting apps and games that I dont use anymore. It still says I can not put the songs on it. It only let me put 488 songs on it. I still have a good 10 or 11GB of space available showing on the bar. WTF is going on? It's a 16GB Iphone.