To expand on JJEgan's comment, if you're not 100% sure it's an official stock ROM, double check, anything other than that will raise the counter and invalidate your warranty.
A little bit about the binary counter: to keep it simple, there's a counter in the device that registers whenever you flash an unofficial ROM, etc. through a program like ODIN. It can be used by Samsung to see if you've voided your warranty or not. There is a way to reset the counter though, and that's through the use of a USB jig, which is a little plug that goes in the USB port of the phone. All you need to do is turn off the phone, plug it in, and the phone will boot into Download Mode and reset the counter to zero. Keep in mind that if you do use the jig to reset the binary counter for the purpose of a warranty return, that it is illegal, so make sure you understand what you're doing before you do it.