60 days grace period on backdated approval

[PVS]

Hi

i changed employers on September last year, they filed the H1B amendment /extension. 

The employer received the approval only today in Jan 2019 with validity back dated to October 2018. 

Do I still have the 60 days grace period to do something about this ? To make it clear, I joined on receipt and I was on the new employer’s payroll till date  

 

Question is, does the 60 day period start from the date of receipt(today) of uscis decision. (Say I have 60 days from today to re -apply for date correction/H1B extension or apply for COS to H4 in case I have a H1B spouse with 140 ...etc)  

 

Thanks for your time