Here, to maybe settle a bit of confusion, I have a more understandable explanation of the system at hand.
As you all know, they have implemented a mix system of Reach and Halo 3. As I have told you, how this works is that they have merged a 1-50 number with a corresponding rank symbol. While I am uncertain if the symbols are all the same as reach, it is the same concept. Now, they have brought back both credits and EXP. Credits are now called "Spartan Points". (yes sova, you were correct). And EXP remains it's original name, obviously. So how it works, is that you earn both spartan points and EXP for each win you get. (spartan points are achieved even in a loss). And, you will elevate in rank correspondingly. Set amount of EXP= rank up to next level. EXP is used solely for ranking up. This is where your spartan points come in. You can redeem spartan points for various items such as weapons, equipment, armor, and other things for your custom loadout.
*EXAMPLE*
You start out as a Level 1, symbol being the recruit from reach. You then earn the set amount of EXP to become a new rank. You then rank up to Level 2, Private. This goes on, 1-50, 50 being inheritor.
I hope this has cleared up some confusion from my original post. I know, OP was not written in the best way. Read this instead.