+BA shows Onhand or Available Quantity on Time Series-P3413

Hello Team,

I am having a concern regarding the Beginning Availability +BA which system shows in the Time Series P3413.

I want to know, is the system showing +BA as a onhand Qty or Availibile Qty.

Refer Below P3413 screen:-

Now if you will see the P41202 Availability screen then it will shows as:-

So from the above 2 screens it seems that +BA is same as Onhand.

Now my concern is, Lets assume Onhand of RM is 100 & Commited Qty is 30 (In WO), So available RM is 70. That means when MRP is ran Based on the Demand for New Items, system should consider 70 as BA rather than 100.