LECOM uses letter grades. An A is 90-100%, a B is 80-89%, a C is 70-79%, and failing is below 70%. We get letter grades for both our pre-clinical and our clinical years (the letter grades on our rotations are interpreted somehow from our evaluation form).
And I agree with DORoe, I don't think it matters one way or the other for residencies. Your LORs will be from physicians you rotate with, and those will give programs a good indicator of how well you performed on rotations. Your Dean's letter will also have the comments that were made by your preceptors contained in it.