jckund on "Question about Pension accounting! Amortization of gains and losses"

So I'm reviewing becker and going through MCQ and came across what I think is an inconsistency.

For gains and losses, it says they arise from two sources: the difference between actual and expected, and actuarial gains and losses.

Now it says these gains/losses must be amortized over time (if in OCI) using the corridor approach, but then on pg 8 and on some of the MCQ answers it says the difference bt actual and expected must be amortized on a straight line basis immediately starting next year.

So the actuarial assumptions are the only ones that use the corridor approach? Or how does amortization work?