H4 Child age out question while awaiting I-485 approval

[Bramaresh]

Need some advise please !!!

I have a son who is studying in college and on H4 visa, he will be aging out in June 2020 as he would reach 21 years of age.
Our I-485 interview was done in the first week of Oct 2019, it is held for review and no approval received yet due to the reason that my Priority Date is not yet current.

If our PD is not current by June 2020, my son would be aging out and I will not be able to claim his as dependent.

I understand USCIS will consider time it took to approve I-140 to calculate the age of a child viz., if it took 6 months to get I-140 approval, it would add that time to 21 years, which means he can be claimed as dependent till 21 year and 6 months instead of just 21 years.  This is as per CSPA act.

Question:

I had my first I-140 approval from my previous employer which took about 6 months time, I left that employer and joined the current employer and restarted the process and it took one month's time to process I-140.

Questions: Would both of I-140 approval time be considered for the purpose of calculating age viz., 6 months from previous employer and 1 month from current employer?

Or is it simply from the current employer??