Pretty sure the estimated days clearly states that it is if you sweep ALL of a ninja's elite instance (including those you haven't unlocked)
In case of Jirobo, there are 3 such instances, and being a 2 star ninja, he needs 30 frags to get. Estimation of 5 days would have been correct, as it would be 3x3=9 sweep per day, 45 sweep total, should drop around 30 frag.
I can't see whether or not there is an updated estimate thing, because I have all the ninjas from elite instance...

Yes, each of the following is same as all of the following.
And when the "following" list all of that ninja's instance, it also means all of that ninja's instances. Did you actually read the "list" of the "followings"?