1. If they told you your contract is for 9 years, that is what it is for. That was easy.
2. So, the package said ROTP much complete 4 years obligatory service after graduation from university. You aren't ROTP, so it does not apply to you. That again was easy.
3. You have finished university and applied as D.E.O. You want to know what the length of your contract is? See No. 1 above. That, too, was easy.
4. Your salary has been highlighted as equivalent to officer cadet, not D.E.O., in your package. You want an explanation. OK. There is no such rank as D.E.O. You will not start off as the CDS, who is a General, but you will start at the bottom, which is Officer Cadet. You will learn all these ranks as you go through your training. You will have some very knowledgeable instructors, with much less education than you, to ensure that you learn all of this. Wasn't that easy.
In the end, you will be given the rank and pay level on your message and if you accept that offer, that will be what you get. Too easy.