WHAT DOES DIAMONDBACK DB15 CHARGING HANDLES MEAN?

Skylar I is going to be calling the moment I get from the field to buy one myself. Quite impressed with the many reviews I've read through. Any army discount. If not I am great with it the value is great.Might be the scope although trigger it used to not be like that. Even about the 40mm I just want to be sure I am able to see reticle nearer to dar