Default Couple of newbie questions..

I have been around drag racing since I was 14 and I am now 42, I have seen and heard some phrases that are new to me in Grudge racing. When guys are betting what does for example 500 on 1500 mean? 1000 on 5000 etc? Also in gambling people refer to a DP what exactly is that? I'm just trying to learn and know what is being said..