How many, less than

I am unable to figure out how to total the number of entries where agents in column 'A' have a time of less than 00:06:00 'B'. So basically I am looking for the amount of times that each agent has a time of less than 00:06:00. Can anyone help?

A B
jsmith 00:05:24
lrogers 00:08:50
jsmith 00:03:52
jsmith 00:09:18
lrogers 00:03:01
jsmith 00:05:02