Changing times into easier data to section attacks in football

Hi, i have some data where the time is in a strange format and i cant use the data easily to divide things into sections. i have attached a small amount of the data and i would like to find out 2 things

1) the amount of attacks which happened between 0-5, 6-10, 11-15 minutes
2) the duration of each attack. (i tried column B - Column A but it doesnt work)

column A shows the time start, B the time the attack finished and C the type of attack

I would appreciate it if someone could tell me how to change the Time data into simpler data