Do not write a full page for section A. No one will read it. And reviewers will shake their head about using the wrong space to get around page limits. In fact do not use Human Subjects, Vertebrate Animals or Resources to get around page limits. Reviewers can tell.
Do use Section A to give some narrative to the rest of your biosketch. Why do you need more time in your postdoc? Why do you need a second postdoc? How is this time going to change your career trajectory?