If you are filling out the AMCAS, you should enter in the semester hours or credits that are listed on your transcript (i.e. 1 semester hour/ .5 semester hour). Most American schools operate on a different system, where a semester-long course is worth 3 or 4 credits, so you should perhaps call the schools you are applying to and talk to them. But I'm almost certain you've got to enter in the number that appears on your transcript.
Ummm...are you filling out the AMCAS? Because if you aren't, then this might not apply 😛