On a microwave, if you push 60, then it will cook for 60 seconds or one minute. (Following me?)

AND if you also press 1:00 it will cook for one minute, or 60 seconds. (Right, right?)

OK! Well, my question is....

If you add 1:00 + 1:00 it is = 2:00 right? So your food will cook for a total of two minutes.

BUT if you add 60 seconds + 60 seconds it will only cook for one minute and twenty seconds. Even though 60 seconds is one minute?

(I know, confusing question.)

I guess to put it into simpliest terms, How come 1 minute + 1 minute = 2 minutes, but 60 seconds + 60 seconds = only one minute and twenty seconds?