H1B Premium Processing start date

I would appreciate if you clarify this for me

USCIS just now sent out an email that they would start premium processing on May 12th.

On the receipt email received by the lawyer it was written “The Vermont Service Center will adjudicate this case within 15 calendar days of the “received date” set forth above.” The received date according to the notice is April 11th.

My question is, Will I get to know the approved/denied decision within April 26 (15 days from April 11) or on May 27th (15 days from may 12th)

Would highly appreciate a response.

What they have said is that SLA for PP petitions is May 27. So it would adjudicated anytime b/w now and May 27.