Backing up the whole calories burned thing. 1600m will at a reasonable pace burn approximately 150 cals which is so very easily by passed with one chocolate bar!
So if you are looking at running for weight loss make sure you have a look at your diet too.
I'd advise writing everything you eat down and using online guides to write down the calorie in take and what you lose through exercise. It will focus your mind on things and make sure you aren't rewarding yourself too much.
As long as you aren't showing any signs and symptoms of problems then there is nothing to be concerned about.
If you experience, faints, near faints, dizziness, shortness of breath or symptoms of feeling overly tired out for no reason then maybe time to get it checked, but otherwise it is your normal physiological baseline.
Everyone is different and just putting an arbitrary figure 'below 60 bpm' as bradycardic is really not helpful. I once took the resting pulse of an ultra runner at 35! He certainly wasn't unhealthy!