STEM OPT Extension start date - seeking advice

Hello everyone,

I'm applying for stem opt extension and I'm a bit confused about the start date. Should I consider the start date for stem opt based on OPT end date or EAD card end date. Or can I consider the start date for my stem extension in between these dates. For context, my opt ends on 26th June and EAD card ends on 8th July.

Any help is appreciated! Thank you!!