Sorry, are you saying 5 plus your age is how many one minute exercises should be done each day?? That doesn't seem to fit with the "5 to abt 15 minutes" per day (and it amounts to a heck of a lot in my case!).
No, I wrote 5 + (age/5)
So first take your age in years, divide it by 5, add to the result 5 and you have your number of one minute exercises to do each and every day.
So when you are 50 years old then age/5=10
add 5 result is 15 minutes or 15 exercices of 1 minute each and every day when uou are 50 years old.