My wife finishes 5G within 10 days by watching Korean drama. Then sometimes she can still send photos in whatsapp (not slow, approx 5-10s send 1) & internet surfing. So, I guess should more than 128k but less than 1M. Of course, cannot watch korean drama in the following 20 days by her plan.
But I need to share 3G data and buy 2 7-days data cards