From the AMCAS help manual:
"Assign Freshman (FR) status to Advanced Placement, Exempt, or CLEP credit awarded when you first entered college. "
Is this credit on your transcript? If yes:
"To claim AP credit, the credit hours must be listed on your transcript. Include AP credit courses only once (indicating AP under the Course Type heading), even though AP credit for the same subject may have been awarded by more than one institution. AP courses can be assigned under the institution awarding the most credit, but cannot be listed under all the institutions that may have awarded credit.
If the transcript from the college awarding AP credit does not list actual course names, enter the subject area for which credit has been earned (e.g., AP Credit: English) as the Course Name."
If not on your transcript, too bad for you:
"Do not send high school transcripts or AP test score reports to AMCAS."
And after they get done verifying you will see a G because:
"The following AMCAS grades do not have a weight or value in computing the AMCAS GPA:G - Used to indicate AP credit not assigned a letter grade."