Understanding how cardio works?

[Ejuicer]

Yor Basal metabolic rate still burns up 70% of your energy at rest, doing nothing laying still, simply making a note of how many calories you have burned on a treadmill is not an accurate way of assessing calories burnt

By doing that cardio exercise, you will be increasing your bmr for the rest of the day as well. That's why it's always a good idea to workout on cheat days in your diet, which a lot of guys tend not to do. This will help to burn off all those additional calories and limit fat accumulation.
You should always do cardio when bulking to keep your cardiovascular system in good health, especially when taking gear since it has a negative impact on cardiovascular health. Doing 20min 3 times a week is good while bulking.

[CapnZ]

If your goal is to burn fat with cardio - you probably want to go for 35 - 40 min at 65 - 70% max HR. Your body doesnt really start mobilizing fat stores for energy until about 20 min into the exercise. You will boost your bmr doing cardio - thats why a lot of people suggest doing it in the morning. For bulking tho - cut back some like Ejuicer said.