MRP PRoblem - Frequency once a week/mth do not work

/hi

I am running MRP wizard. In Item settings I have buing frequency period set to once a month, on the 1st day of month. Today is 22th of Feb. The MRP Wizard reads it well from 1st of March on. It recomends order on 1st of March, 1st od April, Mays, etc. The problem is that it also RECOMMENDS orders between 22th od Feb and 1st od March. With buing frequency period set to once a month it SHALL NOT. Please see the screen below. What is wrong? I have SAP 10PL02