Zerodaze I am sure will chime in here, but I will tell you what I would do.
If you want to trim down, find a speed that works for you and try to maintain it for as long as you can. Generally 20-30 minutes would be good. Figure out how far you are going when a 30 minute run starts to feel easy for you. Then you can start worrying about increasing speed and distance. Most runners agree that you shouldn’t increase your distance by large amounts or too fast because you can injure yourself.
Honestly, just run as fast and as far as you are comfortable with. Anything is better than nothing. You will learn your limits and then you can work off of them.