I'm27l weight 70k i'm not the most fit person but i do exercise regularly. i want to understand about heart rat i did the math it's 199 on gadget 180?

You are probably: Referring to maximal heart rate ( roughly 220-age) and exercise target hear zones. Each zone is a % of the maximal heart rate and is a goal dependent calculation. An example: jogging maintaining a 70% mhr for 40 min will help you for fat burning. Increasing in interval up to 85-90% mhr will improved endurance and increase cardiorespiratory stamina.