Who does win if approvers submit at the same time in case of First Responder Win?

Summary:
Who does win if approvers submit at the same time in case of First Responder Win?

Content (please ensure you mask any confidential information):

I setup as below.

• Approval Group ( Person A, B, C)
• Routing is First Responder Win.

Then when person A and B submit Approval at the same time , I am wondering which person will win.
Because users told me as below.
" we submitted approval almost at the same time. But I definatly submited approval first then other approver submitted e. But other person won."

But I tested myself, the person who clicked "Submit" earler than other approvers always won.