@Taras *********
that is up to the immigration office you use, SO go talk to them and see what they say.
Keep in mind that what we were seeing is IF you didn't get your regular 30 day extension and went straight on a 60 day covid extension they were starting it the day you apply (so if you still had days left on your entry stamp you lost them) BUT if you did get the 30 day extension and then went onto a covid extension it was being added to the end of your extension stamp