difference in dates for specified time

Formula query
Column “A” list of dates correspondence in
Column “B” list of dates correspondence reply out
Need to calculate how many times the difference between date in and reply date is <= 5 in a specific time period.
The start date is entered in say, “K1”
The end date is entered in say, “L1”
Also calculate difference in dates between 14 days and 21 days for time period
Also with reply in column “B” not sent until over 28 days
I have tried SUMPRODUCT with (date_in=K1)*(date_out<=L1) for the dates but unsure how to define <=5

Any help please