ATO - ATP Check for BOM Components

Dear Team ,

I am working with ATO strategy (82 - Assembly orders with production orders)

I have FERT material M1 for which I have assigned the planning strategy 82 & Availability check 02- Individual requirements. And I have ROH material M2 for which I have not assigned any strategy & assigned the availability check as 02 - Individual requirements.

I have created production BOM with usage 1 for FERT M1 & assigned the BOM item as M2.

With this condition, I am creating sale order in VA01. Since this is ATO, the sale order creation automatically trigerrs the the production order with order type PP04. But the problem is while creating the sale order in Va01 for FERT material M1, system through message that  as below (ATP Check - Missing Parts)  for the BOM component M2. But I have enough stock of M2. I could NOT able to understand on what basis system throughs this message. Could anyone guide me here?

1. ATP - Missing Part Details:

2. ATP- Quantity - During Sale Order creation:

3. CO09 - ATP Quantity:

4. OPJJ - Customization for 02 & PP:

Its looks quite strange for me that how come the ATP quantity in the above screen shot 2 & 3 could differ? In screen shot 2 (During sale order creation for M1), ATP quantity as ZERO for M2  (availability check 02 & check rule PP) & In screen shot 3 (CO09), for the same material M2, for availability check 02 & rule PP, the ATP quantity as 310. Why this difference in ATP quantity for the same material M2 during sale order creation & CO09 transaction?

Thanks