Many people were confused with the whole "a" is amplitude but "a" is not equal to amplitude. So Mr. Max changed the notes to say that "a" is closely related to amplitude and the absolute value of "a" is equal to amplitude. Hope that makes more sense.
Mr. Max moved on to the "b" value. This time Mr. Max made the notes clear and stated that the "b" value relates very closely with period. Although period does not equal the "b" value.